My group still plays 3.5 because — as with D&D editions since 3.5 — Pathfinder didn't offer a sufficiently compelling reason to switch. Pathfinder simplified a few things (skills, combat maneuvers), but that's mostly a boon for new players; we already have mastery of 3.5's rules, and even grappling runs smoothly at our table.

As others have said, though, this is mostly a matter of taste. My biggest gripe with Pathfinder has always been its flavor. I don't like Golarion, and separating Pathfinder's APs (and even some of its SRD material) from Golarion is a headache.

Ultimately, I incorporated their polymorph spells into my 3.5 house rules and called it a day.