I'll take the 6 speed over the old 5 speed any day of the week. The thing I didn't like about the 5 speed was that you had to reach really far over to shift into 5th. It just didn't feel right. I'm perfectly happy with the 6 speed. It doesn't bother me at all that it can be a little stiff and clunky once in a while.
The only learning curve when changing to the newer transmission is adjusting your clutch pedal and gas pedal coordination when shifting and learning which gear is best to downshift/upshift into. It's really nothing special.