Both camera flash and Flash, as in multimedia web content work fine for me. Maybe in older versions it was broken? who knows, but anyway
MIUI is closer to an actual OS update than it is a ROM, IMO. Besides the dramatic framework overhaul to the dialer, contact list, settings, android virtual KB, and music player, you can do things like apply themes directly from your settings without rebooting, theme your SMS app on the fly, launch your music player on your lock screen by tapping the lock button, preview SMS or missed calls from the lockscreen, built in screenshot function so no need for drocap or shootme, flip the phone to silence ringer, etc etc
This ROM is basically a combination of many great ideas, obviously inspired the iPhone's UI structure. If I had to come up with something negative to say about it, I would bring up the fact that shortcuts don't work wiyh the default launcher, only widgets. but as with any other ROM whether cooked or factory installed, you can always just go the Launcherpro route.