Re-railing here: I used to have a mini-trampoline myself, and VTam is quite right about it being fun (and easy on the body) to jog or dance on. MGAS, the thing itself is maybe 6 inches high, and it makes you bounce just a few inches higher than you would if you were jogging in place on the floor. You won't be doing any backflips on it, so ceiling clearance is probably not an issue. About 3 feet across though, so room to store it can be an issue.

Linn, anything I can send from exotic California to make either of your lives better? (Note: calamari do not ship well.) You have only to ask...