I will try to keep this review as straight to the point and concise as possible.
This is a great treadmill for the money. Here are a few quick pros about the unit:
1. Unit is very sturdy
2. Quality build and easy to assemble
3. Powerful motor
4. Fitness club look and feel
5. Very quiet motor, incline and running surface
6. Easy to read display (not loaded with gimmics that don't work)
7. 60" running surface (4000i model)
The list can go on, but this covers the most important aspects of it. This unit is heavy, but that isn't a bad thing. The run on this treadmill feels comparable to that of the $6,000 Life Fitness units we used at the fitness club I managed. Do yourself a favor; spring for the 4000i if you can. The metal side rails are a high-end finish and the 60" running board is a must if you are over 5'10". I am 6'2" 210 lbs and I wouldn't have had such a good experience with a 54" running surface. It requires only 72" of clearance from front to back.
Whether you are a fitness novice or a fitness enthusiast, take a very serious look at this model. It wins awards for a reason and has a lifetime frame/motor warranty. Well worth the piece of mind in my opinion.