I haven't done PSA, but I do have the few cards I've had or bought graded by SGC on their registry. Mostly prewar, so all sets I'll never finish and probably won't even get all that close on a couple.
The registry is a nice easy way to have them online, And eventually I'll probably be able to use it as a checklist of sorts since I could look at it with a laptop or maybe the phone.
I would say that since I'm so far from complete there's no competition element, but oddly I found myself comparing that cards I had to other sets in the same range. I was around 60th on the T206 list. with only a few percent complete. (I'm a lot closer, but have only graded a few) When I added the blankbacks and brought the average under a 50 I have to admit a bit of a letdown.
Ha! Just checked the new site and they must have removed a few sets as it's just barely in the top 50 and at only 8% complete.
Haven't tried posting a link before, not sure if it will work.
http://www.sgccard.com/usersetcompos...usersetid=4378
Overall I'd say that if you think it's fun, or useful, you might as well put the set in the registry.
If you don't enjoy it you can always delete it or just ignore it.
Steve B