Hey A., I have an 11 1/2 month old and he's been attending school since he was 3 1/2 months old since I had to go back to work. Honestly, it's been the best thing for him. He's super social, has never had stranger anxiety, is not clingy to just me or dad, and has so much fun at school. He's currently enrolled at Discovery World at the PV mall. It's a bit pricey, but amazing--it truly is a school, not just "day care." They engage the kids, he's been doing artwork since the first month he got there (I literally have artwork he made when he was 4 months old), they have a "curriculum" even for the infants that focuses on developing their motor skills (i.e., showing them how to roll over), sensory skills (allowing them to play with cooked pasta versus uncooked pasta so they can feel the difference and learn different textures), communication skills (teaching them baby sign language), etc. I'm not one of those parents that's hard core about my child being a genius, but my husband and I just wanted to make sure our son wasn't just at a place where he would be changed and fed, as anyone can do that. We wanted a nurturing environment where he would be actively engaged and stimulated, as he's always been quite curious. I truly think that his being in school has a lot to do with his happy nature now--we're always getting compliments from strangers who are amazed to see how easygoing and friendly he is. He also learned how to feed himself early on at 6 months old, and we think this might be because he was watching the older kids in his class eat and became curious about doing it.
Preschool is definitely a personal decision, and as long as your daughter is nurtured, engaged, and stimulated (whether at home or at school) she'll be fine. I just figured I'd share our experience with you. Let me know if you need more info on Discovery World, I'd be happy to provide it to you (we researched several schools and this is the only one that we felt comfortable leaving him at at such a young age). In fact, our daughter is due Nov. 25th and we plan on enrolling her there too!