I have no personal experience with the GSO RCs, but all of the tube versions have the original focuser, which SAGS.
Also, the focuser assembly is attached to the primary mirror cell too, and they are a nightmare to collimate by every single account I've read. You may manage to collimate the scope in one azimuth direction, and it changes under load due to gravity in a different one as you point to a different part of the sky. Even shift of a mm is enough to throw collimation out.
Premium RCs (DSO, Knaeble, PlaneWave etc) are difficult to collimate too, but their mechanical tolerances are far better than GSOs.
note: the truss versions (10" and up) have been re-designed with the v2 focuser assemblies are are much better with holding collimation I believe.
There are a lot of these on the 2nd hand market, and i personally believe that this is because the build quality is not the best, and they are very difficult to collimate. Caveat Emptor.
I base this post on a LOT of research on the GSO RCs btw.
edit: don't rely solo on cheshire/tak collimation devices. Many people are using DSI's excellent user manual to star collimate the GSO RCs and I really recommend that you go with that method:
http://deepskyinstruments.com/truerc...ers_manual.pdf