Ebay will never take the place of going to a record shop or show, etc..., and having the immediate pleasure of finding a record you've been after (or something new & exciting) and walking out the door.
I tend to use e-bay more as a resource for my record shopping that's done off-line. I try to note interesting 45s and then look for them in the field. Generally, with a bit of patience, I can find them for less than the e-bay price. Being on a budget, this is a good thing. Then again, spending the $$ to get a record you've been after the 'bay...feels real nice to mark it off the wants list......