I bought my iphone 4 from radioshack in november 2010, i guess 4-5 months after release. They said they just ran out of stock and could get one from another radioshack in 1 day. I called them a day later and they said come on monday. I came on monday and they said it wasn't in yet, sorry, then they called me 2 days later and said it was in. When they activated it, it didn't work, and they told me to goto the at&t store to activate it.
Long story made short, I don't get excited for pre-orders and I usually wait 2 months or more after a new phone is released to see if there are major pitfalls like battery or maps. I'm not buying it until I see in person and test it out. So far the in videos I've seen online, it doesn't seem any faster than the previous 2 generations and the screen still looks so dim compared to older phones.
Edit: I'd still rather buy it from radioshack or at&t. Apple stores make me feel very uncomfortable just like clowns do. Best buy's are annoying because they use plastic fake phones instead of the real model to play with, and if you ask to see the real thing, they watch you like hawks. Just makes the whole experience rushed and annoying.