I had given away my 3E books in favor of my 3.5 ones, but I recently came back into a set of the 3E books someone was unloading for free, so I still have both. I do prefer the 3.5 books to the 3.0 ones, though.
I never bought the 3.5 books. Just used the SRD online to update my rules as needed. And of course, now that I've switched over to Pathfinder, the odds of me ever buying the 3.5 books are getting slimmer.
I currently have all six on my bookshelf (and multiples of both PHBs), but I voted only for the 3.5 versions, as I'll be selling the 3.0 versions and the 3.5 spares soon as I would never play 3e (as I prefer 3.5) and I haven't played 3.5 in almost two years.
I lost my 3.0 PH at a game years ago and now just have the 3.0 DMG and MM. My local library has a copy of the 3.5 PH I checked out a while ago though. I rely upon the srd for most of my core rule needs and never bought the 3.5 core books.
I never bought the 3.5 books for I refuse to pay $100 for what amounts to a page and a half of errata - and half of it things that didn't need errata. That and the final death cry of the ranger.