I love my ipod touch, it's a great simple to use media player. The safari browser takes a lot of beating.
The downside that I see for the iphone is still no mms, although can email photo's etc. The camera is still pants. I'd be interested to see how well it integrates with Microsoft Exchange, since the earlier incarnations were to ensure the exchange server supported imap ... bit of a cop out there. As, I would expect to see mail, contact, calendar and task sync.
The WM devices are more extensible, and by that nature can end up becoming a patchwork quilt of all sorts of applications. This can at times cause instablility, but I think it's the price to pay for a Swiss Army Knife type device.
TomTom have got their application running on the new iPhone ... but are in licensing talks with Apple.
When I bought my TyTN II, I bought it to replace my phone, camera, ipod and satnav ... but also to include email on the move. I am more than impressed with hosted exchange and having mobile email, contacts and calendar on the go. I gave up using my TyTN II as an ipod replacement since at the time it couldn't sync with iTunes and using the ipod was just far more convenient. I use the sat nav on the phone frequently, but still do not know if I should go TomTom, CoPilot or standalone route when I upgrade! Using it as a phone ... at times is fiddly ... I used to be able to walk along and type out texts etc with the keyboard of my old phone. But with the TyTN II or any touchscreen device, you need to stop ... sent a mail or text and then continue with what you are doing. The camera is a joke, and rather pointless. Before I would frequently whip out my phone to take snapshots, but now I don't bother. It takes too long to start the camera application, and then results are terrible.
I love the nirvana of having one device that does everything ... but I think at present there is no one device which does each task brilliantly.
Sony Ericsson (not including X1)- Great simple handsets, good cameras, ok music players ... poor email support and poor internet support.
Apple iPhone - Great music player, brilliant screen, good phone, good internet, poor camera, no mms, ok email.
HTC TyTN II - Battery time could be better, Sat nav is ok, email is great, internet good, camera poor, music player ok.
Blackberry - Good battery, sat nav is ok, email is great, internet is good, camera is ok.
So I suppose you need to decide whether the device you want is a business centric phone, a camera centric one, or a media centric one.
Sorry for the long reply!