Usually what kills ebay for me is the shipping cost on things like framesets. At my price point, the extra hundred bucks most people seem to be charging absolutely makes the difference between "good deal" and "not so good deal".

That said, I've purchased the majority of my stuff over the last few years from eBay. It is not a quick solution for anything, though... you've gotta have the patience to let stuff go if it gets too expensive.