I'm at 88 right now, with no issues at all. Browser works fine and the camera works fine. Those seem to be the two complaints about low available memory.
I'm purposefully not restarting until I absolutely have to so I can test how low the memory can get on a Tour before it totally freaks out on me.
MeterBerry shows uptime, as well as QuickLaunch's Device info.
Built-in to BlackBerry is the keyboard command of ALT+SHIFT+H, but you'll have to convert that uptime from seconds into hours, minutes, seconds by hand.