Long time iphone user making the jump.

[ZesPak]

Bibbs said:

I see there are some apps to hook into AirPlay etc. Do they work well?
(I've an Air Port Express for music, and an Apple TV)

Yes, but from my experience none of them work as good with Apple gear than... Apple gear.

Bibbs said:

I know iMessage isn't available, but is there anything else I'll miss from swapping?

If you're deep into the Apple ecosystem, you will want to swap to Google. Gmail, calendar and contacts are just simpler if they are in there. It's a relatively straightforward export/import if needed though.
As above, there is no Airplay. We mainly use chromecasts as they work with our iOS and Android devices perfectly, but I know that's not much help.