At This time there is only a full download. There is not upgrade option as of yet. Its been a few weeks to so its not looking good for an upgrade download anytime soon.
Taken from Screw him self
About updating to R9: I am currently sealing up R9, but I've run into a little problem I were aware of, but never expected to actually encounter... The installer framework I'm using, NSIS, does not support installers over 2GB in size... and the updates this time around is about 2.5GB... I'm looking to replace both the installer framework and the patching method, but I'm not currently ready to make the switch, so I'm presented with the choice of just not releasing the update till I've gotten a new installer framework in place at least, or releasing without updaters, so I'm going to go with releasing without updaters this time. I recommend you delete everything EXCEPT FOR THE UserData FOLDER (I repeat, do NOT delete your UserData folder!) and just merge in the new version if you're currently using a previous pack, replacing any conflicting files. Sorry for this, but a lot of stuff here this time it seems.