I never watched it when it was originally aired, but I was to watch tidbits of it every morning on FX. So I decided to get S6, then I got S1. So I watched both of those like 3 times through. Then just this year I decided to get all the other seasons. I'm on my second full watch through. But I've seen S2 three times including this run-through, and I'm on S4 right now. (Hush ftw)
I watched Angel S4 in the morning on TNT, then I bought AS5, then I bought AS4, AS2, and AS1, then I watched S1, S2, and rewatched AS4 and AS5. I'm gonna get AS3 once I get to that spot in my full run-through.
NOTE: I've also watched Firefly one time through, and Serenity twice. Those come after Buffy, then Angel.