I had a 2006 ML 350 with multiple problems. I was interested in a 2010 GL, but just couldn't justify the 85k sticker price with options. I took a 2010 ML350 for a drive and was very surprised at the improvements. The seats are unbelievable, and while everything looks similar to the 2006 model, there are improvements at every level. The ride was always great, especially on the highway, but the 2010 is even more comfortable. The fit and finish is better than any car I have ever owned (previous MB, BMW, etc...)
Seats and steering wheel. They are perfect.
Command drive is not the greatest. Nav has some cool improvements and the voice control actually works, but the interface is cumbersome.