Mixed bag.
As a player, it was pretty good. It gave a lot of options.. I mean a LOT of options since my group had access to every WoTC book. I think I still prefer it as a player than to 4E, especially with the changes that Pathfinder brought about for characters.
As a DM it was a book keeping nightmare by the time the group was level 8. I timed it once when I tried to update a book adventure (Expedition to the Demonweb Pits) to a higher level adventure (4 levels to be exact). I tried to use all the books I had to actually challenge the PCs. It took me 1 hour to modify an existing NPC with a prestige class, equip them, chose spells, pre-buff them and then make their animal companion the PrC grants. Great. Done. Then I had 6 more NPCs, and that was the 1st encounter.
Most people I know that claimed that 3E is very easy to GM ended up ignoring a good portion of the rules and houseruling a lot (much like 1E and 2E). My group tried to stick to the RAW whenever possible. I prefer 4E to 3E as a DM.
All in all, if 3E looked more like 4E behind the screen (greatly simplified NPCs, monsters, and traps) I'd still be running 3E.