I haven't played Borderlands so I have no idea about Borderworlds (seriously, shit name) but I can't say I'm that excited for Fallout: New Vagas either.
Yeah, it's the modern Fallout meets the creators of the original Fallout, except it's not. When was the last time these guys made a decent game beyond Fallout 2 (or possibley Fallout Tactics)? It may be the second coming of Jesus as a lot of people hope but personally I'm going to be pessimistic and say it will most lightly be the Call of Duty 3 of the series.