Ok, so it’s more than 3 things.
10. Loli Otaku Girl and the moe factor.
9. Humor.
8. You can download it real fast-like.
7. A Kyoani anime.
6. Pop-culture references that are not rebranded!
5. Hear songs from other anime.
4. It’s what people are talking about, you want to stay in the loop.
3. Serafuku FTW (the OP).
2. I need fansubs for Hidamari damn it!
1. Lucky Channel.

LOL
~(-_-~)
Seconded on reasons 2 and 8. And maybe 4. :P
Reason #1: Aya Hirano~ ^^
I left that one out on purpose~
I guess it’s 4 & 3 for me. And I guess the lack of (3) may be the explanation for why (4) isn’t enough to get me to keep up with that Gainax thing about drills.
I can’t even claim (2), since I’ve not watched eps 4-6 yet of Hidamari Sketch.