D'oh! I almost wish I had waited before upgrading, now. Though I'm happy with my new Xperia P, I am a clumsy bugger and its aluminium body is quite slippery against the fingers (nothing that a silicone case won't fix though, when I can find one that fits). Also, I do often find it running low on battery... It seems that I might have been better served by this new Xperia Go model.
As the Xperia P is my first smartphone I am far from an expert on these things.
Re ICS, the general vibe on the internets is that Sony are generally good at releasing Android updates for their older phones, even if the 'when' can be a bit vague.