I love Angel. The entire series (with a brief exception at the tail end of S4) is just awesome. I think that on the whole, Buffy is better, but the best of Angel is just as good as the best of Buffy.
Angel himself is one of my favorite leading characters ever, and Cordy morphs into one of the best characters on Buffy or Angel. I'm a huge fan of Doyle and Wes as well too, so I loved it right from the start. I actually think that post-S3 of Buffy, Angel has a stronger overall cast. You know how in a lot of shows once they start adding characters in later seasons the quality goes down? The exact opposite happens on Angel. All of the characters are first-rate. Wolfram & Hart are probably the best overall villains in the entire Buffyverse as well. Plus, Lindsey is freaking awesome.
I love the series opener, "City of". I thought that was a perfect way to start it. They do a great job of making L.A. really feel like another character. And I just really like that Angel runs a detective agency. I think that's cool. I can't remember which episode it is, but in one of the early ones Spike comes to town (he's chasing the ring) and he has that opening monologue pretending to be Angel. That made me laugh so hard I think I almost fell over. "Hero" is one of my all time favorite episodes as well. Doyle's might be the best death in the series (maybe). The fact that that episode comes right after "I will remember you" though was just a double-whammy of sadness.
All the Buffy crossovers were awesome too. Angel vs. Faith is one of my favorite moments of the entire series, and how he saves her was pretty incredible. I love the arguement he and Buffy have later in that episode too, where he makes it clear that he just can't move on from her, and after "I will remember you", where she doesn't remember what happened, it was just so sad.
I was a big fan of S1, but the show keeps on getting better, and it peaks in S5. Trust me, you'll love S2 and S3.