I have a TRUE 525 and as far as I can find out it's one of the best if not the best. If you go too cheap on one of these you will likely regret it. This is another case for buying quality not quantity.
The gadgets attached are fine but it's more important to go for a good sized strong motor.
Mine has an incline feature and I'm glad it does.
I've had several fitness machines from bikes to Nordic Tracks and my treadmill has been the best choice. I've stuck to using it for a couple of years now.
I would also say not to buy one if it's not at a discount. These things are expensive and they have some mark up to work with. Mine was regularly $4999Cdn and we bought it for something like $3700Cdn. I could likely get a large proportion of it back if I wanted to sell it now. I've seen these used in shops at $3000. In other words the cost of owning this machine is the same as a cheap one in the end!
Good luck!