I don't like the style of phpBB3. Although there is a quasi-phpBB2 look available I don't think much to that either. Club XM currently uses it and it's a good place to see it in action. For the range of phpBB3 styles have a look at the Styles Demos on the phpBB Site. I don't like any of them

The main thing is performance and simplicity for me. I think phpBB3 is slow and clunky and does not offer a forum like this any great advantage.
There is no problem whatsoever in me keeping phpBB2 boards running for a long time yet in a technical sense. Although formally unsupported by phpBB now, they're in no danger of suddenly stopping working or having a massive flaw exposed. It's a good, mature product and still well supported by third parties. Ours are also well patched against spammers and therein a question mark still hangs over phpBB3.
My choice would be to remain with phpBB2.