If you're a Firefox user, I'd suggest avoiding Release 30

[thewayne]

The latest update became available recently. I upgraded it on my iMac, put my computer to sleep, came back, and my browser was gone. I thought maybe I'd shut it down to do a Flash update or something, so I restarted it and resumed reading stuff. And a little later it crashed again. Restarted, resumed doing stuff, it crashed again.

All told, it crashed three times in about half an hour. So I went to the Firefox site and found the previous stable release, R28, and have been happily ever after.

So you might want to wait for 31 before updating it.