Mine shifted noticeable smoother after I changed the fluid to Royal Purple Synchromax.
http://www.royalpurple.com/manual-tr...ion-fluid.html
Then I have noticed it get even smoother as a few more thousand miles have accumulated. I have driven a few much higher mileage Camaros and Corvettes and they shifted like butter. So I'm thinking the synchros work better after they have wore in a few thousand miles.
Sometimes on high RPM shifting issues, you are fanning the clutch too fast and it's really not dissengaged all the way when you grab the gear. Try a high RPM shift and deliberately make sure the clutch is all the way in, then a quick gear change, quick but not a yank, and if it still is giving an issue maybe something needs to be looked at. The first step would be to bleed any air out, dealers have a tool to do that. After that, mechanical issues with the clutch or synchros need to be addressed.