The drive would be tolerable if it was rewarded with a great stadium experience - but the one trip I've made to the Trop was a flashback to Continental Airlines Arena circa 2003 when they pretty much left it in disrepair to justify building the Rock.
I'm in Fort Myers, I have the choice of a 2.5 hour drive to the Trop, or 2.5 hour drive to Marlins Park. The trip over to Miami is a bit easier - pretty much a straight shot down on 75 and there are no bridges to contend with. However, the main deciding factor for me is that Marlins Park is honestly the nicest stadium I have ever been to.
If the Marlins could just but a consistently competent team together and win back the fans, they already have the great stadium experience in place.