Not much to add to this thread, but I bought my 99 ML new in 11/98. Out of warranty as of this year, but it hasn't asked for much more than regular fluid transfusions.
Most of the factory anomalies have been corrected during the waranty period, and I too, discovered the harmonic balancer problem earlier this year from this forum and had it corrected.
There is also a recall on the power steering pump clamp, and that should be fixed for free.
Brakes were a bit more complicated to service than the W124 pads, but still a DIY.
Still looks and drives like new!
The 2000+ models have improved interior appointments...I will have to admit, the plastic interior components on the 98-99 series is a bit un-Mercedeslike, and I would have expected more from a $40K+ vehicle when new.
Overall, a fine vehicle IMHO...