i've found the latest version of beejive pretty stable. Not suffered any crashes and getting plenty of push notifications, and not missed any as of yet.
I do wish there was a bit more customisation around the notifications though, as i'd almost prefer it just to say 'XXXXXX has sent you a message' rather than send me 10 notifications if someone sends me a whole load of messages at once.
it does really make me yearn for a truly integrated im solution within the OS though, it would be great if messages came up in a window that i could reply from within, as quite often i'm writing an email and would be nice to give a yes/no reply without having to go to beejive and then back to my email.
That seems more like what Palm is offering with webOS, so fingers crossed apple take note. Iphone OS is so near to being perfect for me but the lack of multitasking is starting to annoy me now.