I've had this bag for a little over a year and it works fantastic.  I use it on every plane trip I use and it fits just fine in overheads.  I'm not sure if it would fit under a seat fine, but I like having more room for my feet, so I've never tried.  This is even a great weekend bag when I do road trips or visit friends.

The best way I've used this bag on plane trips is to hold things like hats or shoes or something that adds a lot of weight.  It really helps keep my check-in bags under the max weights.

My only 2 gripes regarding this item is the wheels don't spin and all zippers don't have 2 pull tabs.  I use the small outter pocket for a quick grab bag and having 2 tabs would make it easier to close with one hand.