Well... first of all sorry if my english is not the best, i'll do my best
Second, i respect and admire the developers team and all the contributors community, this is a wonderful opensource project.
I strongly believe in the phrase " less is more " when designing any interface made for humans. In my opinion phpBB2 is a lot better than phpBB3 when talking about user friendliness ( no matter the template used ).
I think power without control means no power. Personally, as an admin i don't like to have all that big number of "forum toys" installed by default in phpBB3, for example, birthdays, subforums, online-offline, and a lot more. I know there are a lot of admins that love this toys collection and a lot of users too.
But i love to choose what to install and what to not install. This is what i love most of phpBB2.
When you download phpBB2 from this site you download a
Vanilla Forum, when you download phpBB3 you download an overcharged " Vanilla " forum.
The "multilayer" user control panel in phpBB3 is in my opinion too "chubby" for the average user, i consider my self as an almost-advanced users and when i first look to this user control panel i felt, honestly, overwhelmed.
Sadly i think phpBB3 lost the goal of a forum. Forums are a wonderful communication system, people use them to write and read interesting threads, that's the point of a forum. For this i think phpBB3 is not an evolution, is a cosmetic and fetichist change.
I repeat, what i said is with all the respect to the developers/contributors community, i really love phpBB2 and i will not upgrade to phpBB3.