It's no secret the early MLs were plagued w/problems. By '04 Merc was trying to win back consumers and my ML was a great value. All the bells and whistles, no defects, price reflected poor reputation and turned out to be a solid performer! From formal outings to hauling kids, lumber, furniture and landscape rock - still looks good as new.
I enjoy driving this car. It has a lot of power and gets around in the snow and ice really well. We bought this for our daughter 3 years ago, and we've had to replace a water pump, and the brakes, and the tires, of course...but it's dependable and zippy. Does require premium gas. It's a good little car.
I bought my '04 ML350 in june '05 with 18,000 miles on it. I commute about 50 miles per day. I've taken it on about 6 long-distance road trips too. 107,000 miles as of March '10 It is the most comfortable vehicle I've ever owned. Poor MPG (avg. 17.5). Wears out tires every 25,000 mi. Best mechanical reliability I've ever had, despite chronic "clunking" tranny on downshift from day one. I spent $1500 and many dealer visits trying to get that fixed to no avail. Interior plastic skirts around front seats broke early on from pressure of sitting. Coating on all dark exterior metal rapidly deteriorated. I would buy another one if they still made them.
My wife and I purchased a 2004 MB 350 with 32,000 miles on it, thinking we would have a high quality vehicle for many years. We were half right. The vehicle is now ten years old and we have had one problem after another. At 52,000 miles the water pump broke. MB would not stand behind it. Shortly thereafter, we discovered the power steering was leaking. The bearing in the front wheel drive needs to be replaced. Now a light module is defective, discharging the battery almost daily. It's been one problem after another. Buy a Lexus or Acura!
After launching the world's most unreliable SUV in 2001 Mercedes took the ML took this project back and put significant improvements into each subsequent year. The 2004 is a solid truck with great towing, solid handling, great performance for its weight, and an outstanding daily driver. Unlike the X5, cargo space is tall and the cabin roomy. Bumper to bumper length of an Accord for easy parking and tight turning radius. Good in the snow, decent mountain climber and enjoys the twisties! Stay away from the 2001 but you'll benefit from the bad reputation in the following years and get exceptional value.