I usually use an enlarging lens when I use the Graflarger, since I have enlarging lenses and a lensboard with the right size hole. I think it's sharper than any of my taking lenses for enlarging purposes.
The main difficulty with the Graflarger is the ramp time of the bulb since it doesn't have a heater. One way around that is to use a lens with a shutter, so that you can open and close it, but the Graflarger head leaks a lot of light, and I don't think you would want it on all the time. I added some extra baffling around the slot where the neg carrier is inserted to cut that down somewhat. A compensating timer like a Metrolux would be ideal.
If you use VC paper, you might want to add about a CC40Y filter for more linear results or when Aristo figures out what they're doing since they were bought out, you should be able to upgrade the bulb to a V54.