We only did preschool for a very short time... and it as dh's idea, not mine. My 5 year old at that time was 26 months. He was in an "advanced"

preschool for 18 mos - 5 years, and their claim to fame was that sometimes their kids were able to go straight into 1st grade. My 26 month old was already reading, though. He already knew colors, shapes, numbers, etc. Didn't matter, though. They sent home a progress report telling me he didn't even know how to hold a cup. He was terrified of that place. There was only one teacher he liked (of about 4). He didn't like any of the kids, and he certainly didn't like any of the "daycare" rules (like kids can't touch the books because they're only for teachers???).
Personally, I don't think preschool is necessary for anyone unless they have some type of special need that should be addressed before starting school. Yes, I'm a homeschooler, but I'm NOT an anti-schooler (as in public school). I'm a former teacher myself. I know the public and private schools have their pros and cons just like homeschooling does. However, I think homeschooling is usually the best option at the preschool level. There are so many things that can and should be taught at home, and besides, your children are truly "yours" for only a very tiny percentage of their lifespan. If your daughter lives to be 80 and you keep her at home with you until she's 5, you've only been the major influence over her for 6% of her life.
I don't get offended when people don't agree with me, so you're welcome to take this or leave it.

I just think she can learn much more through library storytimes, local art classes, playdates with familiar friends, and things like that than she can being stuck in a room with 15 other kids putting up with those kids going through their potty trainings, biting phases, hitting phases, etc. No privacy or encouragement when going to the restroom (my son was already trained, but he regressed after seeing what level of training he was "supposed" to be on with other 26 mo olds

), and on and on... She'll pick up on what the other kids are doing and become part of a pack heirarchy. She won't be free to learn whatever her interests are. You'll learn more in the first 5 years of your life than you'll ever learn at any phase of your lifetime. Why waste it?