Go with the biggest DC motor, widest belt and most steel you can find/afford. Prioritize on these then look at the gadgetry
A True Model, the LifeFitness Model 7 or better are the two that I was split between. I went with the LF Model 7.0.
There a a 'consumer reports' type site - ignore it. It only pushes you to a certain brand and when you dig through IP addresses, you will see that the alleged CR is owned by that company. Runner's World has an annual breakdown.
You need to get up early and head to a Sports Store that has inventory plugged in. Bring your runners and spend 3-10 minutes on mills you think you can afford. I think I spent 3 hours in the store before narrowing to the two I liked best. You need to push speed out a little faster than a long run pace and you should also cycle your run from 0% up to 4-8%. Usually by 4% you will get a feel for that uneasy bounce. This is probably the test that will rule out the most units. It is also important as you really want to run at a 1-2% inclines on a mill to negate the motor effect.
As far as gimmick(gadgets), you really do not need these. It may be nice to have a fan in the control panel, but really, you are going to put a fan (or 3) in the room to move the air. A mill will make the coldest room hot in an hour. Though, I will say that a feature on the LF model helped push it in my mind. Most mills come with a max time of 99:59 before powering off. The LF has marathon mode. You can start the belt then push the time to marathon mode and it will run until you give up.
Hope this helps.