pwdebbie, we were in a handicapped room both ways on our trip last summer. I am not in a wheelchair though I do travel with an
ECV to WDW, and use a walker when I go out. My disability is also invisible though I used a wheelchair to and from the train car (it was a long walk!). I reserved the room when I made our reservations (note: you can't do it online; you have to talk with someone).
I posted pics of the room a few pages back. There is a curtain that separates the "business end" of the roomette from the sleeping/sitting area.
The positives: the room steward does get all your meals for you (and I tipped accordingly), and also makes up the room. The roommette itself was very convenient. Only a few steps INSIDE your roommette to the "facilities."
The negatives: the beds are very hard. My son was able to sleep. I dind't fall asleep until around 4 or 5 in the morning as I was so uncomforable. Maybe bringing a foam topper would have helped. I also definitely would bring pillows and a light blanket next time around.
My teen slept on the top bunk. There is a net of sorts that "keeps you in." However, depending on your own mobility, sleeping on any of the top bunks might be an issue.
I have thought about travelling coach our next Autotrain trip (post-surgery I sleep in a recliner so this may not be so different). I have found in my reading, that a steward will get food for you as well if you are travelling with a disability (visible or not).
Hope that helps!