I like the latest one, the one that says the full name, but I don't think the tag will hold up well when reduced to 57x57 pixels. I'm not sure that adding "best" helps with what an icon is supposed to do... it's like it's trying to do too much. I would just lose the tag and keep the rest as is. It's simple, crisp, informative. The single F, although different in appearance, is a bit similar to the Facebook single F icon. I also think the color is very distinct and will stand out without being gaudy.
I think drelbs is correct that Apple will not approve this app, so none of the Logos matter. A dev posted about this and in disgust realized he wasted a tonne of time. Please don't quote me on this since I am not 100% up to date on what happened!
