So! How wide are the aisles?

Just about wide enought to bring anyting you want I guess.

We just took the train from Rome to Florence (1st class) and there was ample storage at each end of the car for luggage as well as overhead. It was way more roomy than any of the airlines we flew!

I agree, first class is a different story.
The on/off question is a big issue.
My wife and I have learned to anticipate getting off, and before we arrive, we get the luggage into position.

Once the train stops, one of us gets off the train and the other one ands the luggage out.

Those rolling pieces are heavy before you put anything in them! I think my wife's weighs 13 pounds empty.

I got a cheap, light one, figuring that if it comes apart, I throw it in the trash bin and get another one. I carry a roll of duct tape for emergencies.

So far the budget model from a major department store has lasted better than its predecessor which was much more expensive and sold under a well known name.

eurogals touches on a good point. i think having more luggage than you can easily manage opens up potential safety issues, that you would not face if you look competent and in-charge and are able to easily manage your own things.