I heartily endorse the "try before you buy" philosophy. We've had 2, both Nordic Trac. The first had the normal type running bed. I'm guessing the machine was a lemon as even the technician gave up. When they offered replacement, it included a better model with the reflex bed. What a difference!!! over the years we put over a thousand hours on it, both wife and I used it. She used it for therapy and always very slow speed, maybe topping out at the 3 of 12 setting, time was her goal, like an hour plus. My goal was usually distance in a certain time, where once I made my time, like 30 mins, then increase how far I went in that 30 minutes. It was actually pretty kind to your knees and legs. Eventually, the electronic board went out and as it was way out of warranty I refused to replace the board and gave the unit away.
We replaced it with a Bowflex treadclimber. Very different workout and we both "like" it. I gave it up a bit ago when my knee got too bad but am hoping to work it into my rehab after I get my new knee.
Both the treadmill and treadclimber I find absolutely boring. Thankfully the treadclimber takes less time.
I'm thinking of taking Bird's advice and getting a recumbent bike.