Not with the new MacBook Pro machines. At least not until you've watched two movies. I can get over 7 hours of battery life on my 17" MBP. Using the higher power discrete graphics chip is going to shorten battery life, as will doing something more intensive like 3D gaming.

The removable battery user group is some 1% of notebook owners - this isn't my stat, but I can't recall where I grabbed it from. Some of that 1% will be taken care of by the much longer run times with the new batteries.