I have the SLVR L7c (Verizon) and it does have the mutilated UI. But I can confirm that the phone will play mp3s and 3gp encoded videos. But beware, it's not a music phone even though it has that capability. I rarely will even fire up the music player anymore. Verizon has much better choices if you want a music player phone (the new LG Chocolate might be a good choice - it supports up to 4GB TF whereas the L7c and most others only support 2GB). Also, the L7c only has a VGA camera (WTF?) which will do in a pinch, but it really sucks.
Overall, I'm not really sorry I went with this phone; it's definitely not a bad phone. It's just that my heart really wasn't with the phone anyway, and I plan on switching to AT&T for an iPhone when this contract comes to a close. I basically bought this phone because it was cheap and it wasn't too bad.