I'm so partial to the Dow in Saginaw because I just love how you can walk/stand all the way around the bowl and still watch the game. There's other things I loathe about the home arena but that one feature makes a hockey game very watchable.
Of the other arenas I've been to (I've been to 10), I really enjoyed Peterborough...the people, history, etc. were great. We also had a really nice time in Hamilton...we splurged and sat on the glass for that one so to me, we didn't get a true feel of the arena but the people around us were fantastic.
I would agree with Kingpin on Kitchener, for us, it was probably the least "fun" experience of the 9 away venues we've been to. The fans were there for hockey which is totally fine but there wasn't any "hey, you traveled 4hrs to our town, thanks for coming" sort of vibes which we've had even in Sarnia/Windsor. I'm very happy to have visited and watched a game in that great venue but it's not one I would return to.
Worst arena I've been to...Compuware (Plymouth Whalers)...sight lines were terrible and despite the successes they had, just didn't feel the energy of other OHL arenas.