I've found 530 to be very stable.
I'm surprised no one has posted about the BES mailbox FINALLY being separated out from the Messages mailbox. This is great but was a LONG time coming! Big thumbs up.
On the downside, the browser seem to load pages faster, but seems pretty sketchy in terms of link clicking. Really sketchy in fact. Lots of clicks on links seem to go unrecognized.
Also, my BB seems to have gone through an entire battery today despite very light use. That's a concern.
Otherwise, things seems very stable and very, very fast for me.
9630 #4 < 9630 #3 < 9630 #2 < 9630 < 9530 (returned) < 8703 < 7250