Well I've been playing with iOS for a while now, and at first glance I'm very impressed.
SIRI actually does something now apart from dial numbers, you can get it to find shops, types of shop, takeaways (very important) or just ask how to get to xyz and it'll give you a map. Unfortunately, despite being told to go there several times, it doesn't know where Hell is, but can give me 14 places called Heaven nearby (I daren't look).
If you use your PC/iTunes to update you do need to make sure your backup is in place, but straight from the phone it works fine and carries on where you left off.
Once you've downloaded it you do need to have a minimum of 50% battery (or be connected to a power source) or it won't install (yes I've installed this on several devices in different ways).
It seems to be a little bit quicker and smoother, but that might just be me, the resolution is definitely sharper though.
The EE symbol (Everything Everywhere) in the signal bar is a bit strange, I'll find out soon how much quicker it really is.
It doesn't ask for your password for app updates any more either, and I've heard that you don't need it for free apps either, but I haven't checked that yet.
It has frozen once partway through app updates, but pressing the power key for a second took it straight out.
The new maps icon looks a lot like the old Google one, but is totally different, I'll try it as a sat Nav tomorrow and see if it's saved me the cost of a TomTom app.