Treadmills- Should I own one? Review

after recently undergoing gastric bypass surgery it is reccommended that I do some sort of exercise daily.  With an existing back injury I am limited as to the type of exercise I am able to do on a daily basis. So, after some discussions with my doctors it was unanamously agreed that a treadmill would be the best and safest form of exercise that I could do on a regular basis without further injury to my back. I have been researching all types of treadmill and have yet to decide upon the best value that meets my needs.