Sluggishness in handling or sluggishness in acceleration and climbing?

For the latter, I'm guessing that the two bikes you rode have bottom brackets built for someone like me (I'm guessing you and I ride near to the same size bike - at least close enough for horseshoes). Bottom brackets are where you get that snappiness in acceleration. A good custom builder will use different tubing to tune (uh, beef up) the bike's bottom bracket to the rider's weight.

Then, there is the whole discussion of acceleration from wheels. Argg!

What do you want from the bike? If you were telling a builder in your own way what you want, what would that be? What riding characteristics do you not like about your own bike?