I meant soft bag as opposed to suitcase which is more bulky even if small

???? Is this anything like 'Snakes on a Plane'''?

I like wheels. Their a pain when there are no stars, but still, I've rolled my suitcase all over Europe.

If you are wanting to know if it is a problem to take your luggage onto the metro, the answer is "not really".
You will have stairs and tunnels to navigate, and some metro cars can be very crowded at certain times. You need to position yourself such that no one can grab a bag as the doors are closing and make off with it.

also, need to mention that you have to get yourself and your luggage thru various types of turnstiles when entering the subway system...

Every station I can think of has some sort of bypass for luggage. Here's an example:

http://france-tourisme.net/photo/cal...R-CDG2-4_M.jpg

For large "things", there is often a gate across from the ticket booth that the ticket seller can open.

<i>Vraiment!</i> One can even take bicycles into certain trains at certain times/days of the week through the <i>portillon de service</i> alluded to by Gretchen. On the RER, it's basically any time except weekday commuting hours.

http://www.ratp.info/informer/bicyclette.php