What level are you starting at?
You have run 3.x, so as long as you were fine with that, you should be fine with Pathfinder. At 1st-level, wizards are stronger, which is cool, due to specialists getting X 1st-level-equivalent spells (as spell-like abilities) per day, finally fixing that "wizards using crossbows" problem.
The standard point buy seems to be different. I'll illustrate an experience you may wish to watch out for. It's not necessarily a Pathfinder-specific thing, but could happen more easily in PF. At 8th-level, one of our players retired his rogue character and showed up with an elf necromancer. In an act of "no social skills" (very surprising for the player, who is an amazing DM, although not of D&D) he brought in a character without any sort of preview on our mailing list or wiki. It was a core-only elf necromancer. In 3.0, the standard point buy was 25 and a typical PC was expected to start with a high stat of only 15. There were no races at the start with any mental stat boosts. (I seriously doubt any group ever played a wizard with starting Int 15, they'd nerf Strength and Charisma and even Wisdom to start with a high stat. Playtesting is supposed to catch stuff like that!) Our DM has us playing the equivalent of 32 point buy (I forget what this is called in Pathfinder). The player's character started with Int 18, +2 for being an elf, and then of course +2 for levels and a +4 item, giving him an Int of 26 and having save DCs of 18 + spell level, plus had Dex and Con scores high enough to not suck. Said PC started curbstomping any and all encounters viewed. Said player is always paranoid of their PC getting hurt and so took all the best defensive spells (always either invisible or mirror image'd, the latter getting a buff it didn't need in PF)... and if they'd been more familiar with 3.x/PF rules and had taken Spell Focus once or twice, would have been even more overpowered.
I would say take 15 point buy (that's the equivalent of 25 point buy), but the high point buy made PC concepts like my druid wildshaped-focused PC vastly more viable than would normally be the case... certain types of cheese are just easier or at least less costly in PF than in 3.x.
I have never run Pathfinder, but I used to run 3.x and have been in two Pathfinder campaigns. (Currently I'm in Kingmaker.) Do yourself a favor and don't allow a lot non-core books, classes or archetypes into the game. Our DM lets us play anything, and there's been quite a lot of cheese, not counting the necromancer all-core example above. We have a barbarian/alchemist, the latter synergizing scarily with the former (especially with the ragechemist archetype), since they're all similar but differently-typed bonuses, plus the barbarian is the armored hulk archetype, taking away the barbarian's only real weakness compared to the fighter. He's dishing out more than a hundred damage as round, and has an incredibly high attack bonus due to the three or so different kinds of Strength bonus he can aamss. This was in stark contrast to the bard/cavalier, who wasn't even as good in combat as his horse. (The player switched to a magus, but using the same character, so he had to give up the horse. My druid then awakened it, terrifying said PC.)
Or perhaps talk to your players about what's crazy and what's not. Learn those first. Between all the new classes and the large number of archetypes, it's not possible to be familiar with all this stuff at start.
Last piece of advice, there's this nice product called the NPC Codex. I prefer 4e to Pathfinder, but Paizo has a much better understanding of their market than WotC, putting out adventure paths and the NPC Codex, which sell like hotcakes. Even though I don't run PF, I bought the NPC Codex anyway, and mine it for 4e NPC ideas. I'm jealous. Since WotC has stopped printing 4e, there's never going to be a 4e version of the product. (Well, not an official one anyway.) NPC generation takes a very long time in 3.x/Pathfinder, and sometimes you'll need an unexpected NPC right now.
