Same 6bit active matrix specs as the Duo 280 there. The additional 640x80 strip of pixels might almost make it worth carrying the additional size, weight and taking the 4MB max RAM hit, but that awful trackpad is a deal breaker for sure in my book. There's also the appearance challenged aspect of the 540 to consider. Luckily, that offshoot of PowerBook design died aborning. The Blackbird was in a class of its own in terms of industrial design, but that's a matter of taste. In terms of a PPC upgrade path however, the 2300c MoBo swap for the Duo 280 is superior in every way to the 540's PPC processor card swap.
Duo's rule! ;D