Apple should clearly state before installing the software that you won't be able to receive genius bar service. Better hope your lightning connector isn't the first thing to malfunction.
Apple clearly states that iOS7 is for development purposes only and that you should not install it on a device that is required to work. It's like line 2 of the developer agreement. A genius bar is for an end user to get help. Developers are not end users.
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They're being a bit ridiculous with the servicing part though.
I took my development phone (which was running iOS 7 since it's used soley for development) in because it developed a massive white spot on the screen. When I checked in, they made me physically sit and wait while it restored back to iOS 6 before they'd even see me.
If it's a glitch/could possibly be a software problem, fair enough - but all it did was piss me off - there's no way a white spot can be software.
Just restore it back yourself before you go, not a huge problem....