I actually had something really really strange happen to me on Monday. I was home, and i'm always hooked to wifi home, and then when i leave out of range, my phone jumps to 3G. I rec'd an email right before walking out the door. I fig'd i'll check it at my next stop. Arrived at my destination, parked and grabbed my 4S out of my bag. clicked home button, slid to unlock and then tapped my mail icon to read my email. Well, the icon literally stayed lite blue for a good 5 seconds before finally going into my email. From there, i clicked on the acct i wanted, and the 'acct name part' of it stayed lit up blue for a few moments again. When it finally decided to open to the actually email list, it did it soooo slow. it was like the screen was moving in slo-mo. I tried to open the email and it froze again. At this point, i decided, let me just back out to the home screen and then go back into the email. Well, no dice. the screen froze completely. it wouldnt respond. i had to do a reboot (hold top button with home button till seeing the apple & then let go)
So my phone rebooted, i was then able to access the email no prob. I know for a fact i did not have alot of apps open, maybe just my phone calls and text msgs. it was really strange, but since then nothing happened like that again. I did ck my diags log, and it shows a LatestCrash.plist for MobileMail on the day of 11.29 with the time it happened and all sorts of codes etc. although i DO NOT send my diags&use to Apple.
since then, knock wood, nothing else is listed TG !!
So, yes, i've experienced the 'slo-mo' screen. If this happens again(hopefully wont!), i will call Apple about it being i do have AC+