Tim,

In the last 11 months since I bought my ML, I've added (in order) the Nav system, Timeport phone and 2002 bi-Xenon lights. Here's my logic, your needs, likes and checkbook may vary.

NAVIGATION.
Regarding the NAV system, over the past 3 years, I've run a handheld Magellan ColorTrack GPS alone and also tied it into a 15" display laptop as well as a separate DeLorme Earthmate GPS with a Sony CLIE palm device. Both setups gave me realtime moving map navigation with some advantages and disadvantages of each.

First the laptop. I needed to run a power inverter, or do laptop battery management. The moving map display on a 15" LCD screen is great, but can be too bright at night, and it also fills the front seat, so whenever I have a passenger, it's not good. You also have to provide aux power to the handheld GPS. You end up with a lot of cockpit clutter with cables. Its also hard to safely secure a laptop and GPS without some type of seat-top workspace device. Route entry is about the same, with the advantage that I prepared routes at my office on the laptop ahead of time before traveling. The databases available from DeLorme are pretty good (using Street Atlas 6.0, 7.0, 8.0 and Deluxe over the years). The laptop is not flexible for re-routing or off-route performance. The nice part with the handheld GPS, is that I could detach the unit and go hiking / hunting with it. Accuracy of the system was outstanding , with surveyed errors on the order of 3 ft and was strictly a function of Selective Availability being turned on or off (it was turned off permanently a couple of years ago - the one good thing Clinton ordered). I could use either the Magellan ColorTrak (around $275) or the Earthmate (about $125) for the laptop. That, plus the cost of Street Atlas ($50), a DC/AC inverter ($50), and some cables ($20) and excluding the cost of a laptop you're in business for under $250.

Wanting something smaller, when I bought a CLIE (palm OS), it was compatable with Street Atlas. You have to add Solus, which is an application that clips maps from Street Atlas and saves them as files you can display on a palm OS hahheld. Bascially, you use Street Atlas to select and crop an area from your map display, and save it as a file which is downloaded to the palm CLIE and viewed through SOLUS (the palm application). As with the laptop, I got a moving map display and good street level detail in small areas, but the memory limitations of palm devices (8MB) result in you having to select either a small area map or an unacceptable low level of detail for longer trips. With the CLIE (color backlighted display), I could get about 4 hours of operations on a battery charge (Lithium Ion internal rechargeable), and 10 hours from the Earthmate (4 AAA's). The CLIE / Earthmate system was a fairly basic solution, and its biggest advantage was it was a space saver. The Earthmate sat on the dashboard, and the CLIE rode in a dual Palm / cellphone holder suction cupped to the windshield. Route planning and map selection is done on the mother computer that synchs with the palm device, and there is no off-route redirection capability.
Costs run about the same as the laptop hookup, because instead of getting an inverter, you need to buy SOLUS. DeLorme had a package with Street Atlas, Solus, and the Earthmate GPS receiver for under $200, and you get a $20 cable. FYI - the Earthmate has no display, it must be hooked to a computer or palm.

DeLorme just announced an upgrade to Street Atlas and Solus, where they now have one product called XMap Handheld Street Atlas USA which can be seen at - http://www.delorme.com/xmaphandheld/default.asp
- this combines the two previous applications into one, plus allows you to clip larger maps by using removable memory devices such as the Sony memory stick to load your database, which the palm application can access directly. Previously, you had to load maps to the internal palm memory (limited to 8MB for all applications and data on the palm).

So, back to reality. After using both these options, I decided to do the MB NAV upgrade. I wanted the following functionality.
1. A cleaner cockpit with no cable clutter. Less crap rattling around is a good thing. Wife refused to have laptop sitting on her now non-existent lap.
2. Better off-route redirection and responsiveness from the system.
3. A better database of addresses, telephone numbers and points of interest.
4. A right sized screen (palm was too small, laptop too large)
5. On the fly activation, deactivation, and route planning.

I am a licensed pilot and former Navy Fleet navigator, so operating a vehicle while doing other tasks is not excessively challenging. Cockpit management is the same the world over! My dealer quoted me about $2300 for installation, and I was able to get the MB system from Clairparts with costs as listed:

Nav unit - $1300
10 Nav Disc CD pack - $270
Shipping - $15

Dealer install - 1.5 hours - $140 (incl tax)

Total - $1735

This compared to the best local dealer quote range of $2200 - $2395 for their package (with only 1 CD, not the entire set).

So, I made the decision that the cost was an acceptable factor for the functionality I was buying. I don't use the voice nav capability, but have found the onboard database handy for finding gas stations, specific resturants, a branch of my bank while traveling, and telephone numbers of various businesses I wanted to call while on the road. Even though the nav routing may direct me on a route I don't want, the off-route recalculations are very quick and are helpful in getting me where I want to go. What I miss are being able to display are the satellite constellation and status, as well as a current lat/long, course and speed. That's the navigator part coming out, becasue I can often tell based on the number of satellites and their geometry how good or tenuous a fix will be. The MB system tracks much better than the others, due mostly to a "snap to" feature where the system pulls you onto the nearest road if their is GPS fix "float". Also, the vehicle has an internal gyro, which I believe also feeds into the ESP steering assist system, as well as provideing gyro inputs to refine satellite fix data. I am very pleased with the system despite the cost.

Regarding Lebenz's post, I agree that there are other functional solutions available. A dashtop unit like the Garmin Street Pilot may meet your needs. I'm planning on keeping the ML for a long time (had a 240D for 13 years), so upgradeability of the database was a factor in choosing a CD based system. The Garmin's are a good small sized and accurate stand alone system at an ever lowering price point. They can be hard wired for power and I believe the databases are upgradeable. That might hold you until you decide to trade your '99. The 2003 ML NAV sytem is going to be DVD based. I don't believe it would be cost effective to upgrade a '99 to th MCS system, it may not be possible because of the switch to fiber optic wiring in the '01 that I have. The connection between MCS, NAV, the antenna, both cell phones (TeleAid & Timeport) is a technical nightmare.

Continued on next post . . . .