Well, in the games I'm in at the moment, it's as follows:
Rolled stats (4d6, drop lowest): 1. Although the GM's said if he does another game once this short campaign wraps up, he'll have everyone else roll and then assign me points based on their averages, because I tend to be the luckiest (bloke) on the face of the planet when rolling stats. (The look on his face at the stats I rolled in front of him..not one below a 14!)
32 point buy: 2. Both fairly standard games. Another one starting up soon with 32 point buy, and I'm running one anon which is 32 point buy also.
40 point buy (!): 2. One of these is less a 'game' and more a hack-fest, where people can try out their 'broken character of the week.' I turn up every now and then.
The second's my current favourite game; a scary campaign of great magnitude, where we may have the end of the world occuring in 9 months time, the secret police of the empire (the ones with carte blanche to do whatever they like) are seeking our heads on spikes for poking into matters we was not meant to know wot of, and we're having to pretend to be a travelling circus to disguise ourselves (oh, the humanity!). Did I mention we're travelling with a wild mage we can't seem to get rid of? (every so often, he tries to 'help'. The party ducks and covers.)
The level of this game, you ask? 4th. With the equipment of 2nd to 3rd level people. (Only magic items in the group: 3 Handy Haversacks, 1 set Gauntlets +2 Str. Getting the gauntlets off the super-l33t bandit leader of doom was no picnic, either.) The GM said '40 point buy. You're going to need it.' So far, that's been nothing but the truth. And it's one of the most fun games I've ever taken part in.
Generally, I tend to go for 32 pt buy. Rolling may seem fun, but too often I've seen one character with really good stats eclipse people who haven't been so lucky. 32 points makes you significantly above average (as I tend to feel adventurers should be), and more importantly, equal. 28 pt buy can also be good; it genrates more 'human' characters, unlike 32 pt where you don't have to have a below average stat (unless you're a dwarven barb of charisma dumping doom, of course. Has anyone ever seen a dwarven or half-orc barbarian built on points buy with a Cha above 6? The Public Has A Right To Know!

). 32 pts, you're significantly better than John Q Public. Heroic, even. 28 pts, you're still pretty damn good, bt those 4 pts can make a surprising amount of difference. 40 pt buy; well, without extra penalising factors being added in (see comments above), it tends to feel a bit overpowered, especially when people return to 28 or 32 pt buy. ("What do you mean, I have to have a stat below 14? I never have a stat below 14!") There's a difference between heroic and silly.
Just my 2 cents
Synchronicity.