I have an older commercial Trotter (now Cybex) treadmill. It is very powerful and I bought it off of ebay a few years ago. My dh, my older kids, and I use it. It can withstand about 300 lbs., it's quiet even running on it, and it's heavy. I've had it serviced twice now just to keep it maintained properly.
On the fitness boards I frequent (I am, after all, a fitness freak

) many people are also pleased with their Proform. It's one of the popular models yet I have also read that it depends whether you run or walk on them because they can get noisy and some vibrate too much if you run. If you plan on running intensely and regularly than you'd probably want something more powerful, but since you plan to walk on it I think you'd be okay with it. I would try them out if you can to see if it will work for you. I know the belt space to run/jog/walk may be very limiting for some people, too.
My sister has one and it has those functions, like heartrate monitoring, but I think I read (Consumer Reports or a health site?) that the monitoring is not as accurate as a conventional one.
You might want to check the reviews in Consumer Reports because they recently rated the newer models. They mention noise, durability, etc., but they didn't rate Starbucks and other popular products like the Dyson vacuum very highly so I always take that in consideration.
As for ellipticals, I have a Bally's one and I use it more than my treadmill. I think it's more fun because you can rotate backwards and it's easier on my joints. Of course, some models are more stable than others and the "stride" length (?) is comfortable. I would definitely try some out at the store or see the ratings so you don't end up buying a coat rack. lol
Hope this helps
