Fran, we have an elliptical and its a killer for me. I think the fact that I have short legs and thus a short stride makes it more difficult for me. We have one that can be elevated, not sure if all have that feature, but I know others who swear by it and it is much milder impact on joints. When we bought the ellitical the guy said the ones with the moving arm handle bars were a waste. He said that it didn't really work your arms and it would be better for your arms to do some weight training. I can barely chew gum and walk, so we have stationary handle bars.
Since I don't really glide on it, it seems much more like jumping along and I can only last about 10 minutes without keeling over.
We used to have a rowing machine at the place where I worked out and that was great. It was however, very noisy. There was a fan on the front that cooled you off, but was loud. I haven't used any newer rowers, so couldn't tell if they have improved, but I did love it because you could do arms and legs at the same time.