Agreed. I RMAed an Intellimouse 1.0 two months ago, and got a Intellimouse 3.0 as a replacement. It's smaller, and the back/forward buttons are hair-trigger sensitive. If the "feel" is very important, I would recommend just going to Compucentre or somewhere and just hold the floor model in your hand.
But you know, they delivered my new mouse in three days, and they don't require you to send the old one back, so why not just issue the RMA, tough it out for 3-5 days with the old mouse, and then receive an Intellimouse 3.0 for free? If you really hate it, just sell it.