I've only second-hand experience of the HTC TyTn II as my boss has got one, but I've got two TyTns (T-Mobile MDA Vario II); one of which has WM6 installed (I've used a few different versions too).
First things first, as a gadget it's great, and depending on your needs can be damn useful. Having said that though, if you're going to use this as your primary phone which you will use quite a lot, it might not be the best choice. Don't get me wrong, I couldn't be without my TyTns - but I DO NOT use either of them as my 'phone'... I use my phone quite a lot (I get through 3000-4000 minutes a month, and while a lot of people will use more texts than me, I still get through a few per day) - and because of that I like them to be quick responding and easy to use. My last few phones have been Sony Ericsson and to be honest I can't fault them. The OS/UI is always well thought out, they're responsive (you can fly through menus, phonebook, writing text messages etc.), hard-wearing and just no-nonsense bits of kit. The same can't be said for the TyTn though - as a phone/SMS/MMS device it's a lot more clunky. It can be slow to find contacts, dialling numbers is painful as you'll tap the digit on the screen and after what seems like an eternity it'll be added to the number you dial, and messaging can be a little slow/fiddly too. Things have gotten a little quicker with the TyTn II thanks to its slightly different hardware setup, but there's still not a massive difference between the devices on the whole. You can for example, flash a TyTn with a firmware freely available on the web which will give it pretty much all of the TyTn II features - including the pretty homescreen and TouchFlow. The only real differences after that are the camera resolution, the built-in GPS (and for the record the TyTn (mk1) has this chip on-board too, it's just that it's invisible to the OS and the antenna pins are shorted together), and the pop-up screen.
I'm not trying to paint a terrible picture here, as I've said - I couldn't be without my TyTns - but I only use them for a) mobile web-browsing, b) as a modem for my laptop, c) mobile email (push email - similar to Blackberry) and d) to some degree as an organiser. For those uses it's a really great piece of kit, but if you're quite demanding in terms of the performance of a phone when it's being a phone - in my opinion it falls a bit short.
I don't know what your 'phone' needs are, but in terms of pictures and video the TyTn is average - even the new camera on the TyTn II isn't as hot as others of similar spec. It's pretty good for watching videos on though - you can throw VLC Media Player at it and it'll play almost anything. It will chew the battery though if you have the screen brightness at a high-ish level.
Out of the others you've listed I'd say the K850i is a good choice - the difference between it and the W960i in terms of music support aren't massive in real day-to-day terms. I guess it'd still do all the music stuff you could want, just doesn't have quite so many of the 'trick' features. The camera on it is pretty damn awesome though. It delievers pretty crisp pictures, and considering it's still a phone at heart, has a lot of control for the camera - right down to ISO sensitivity. The OS/UI is good as is to be expected of SE, and it'll handle phonebook/call/messaging stuff as fast as you can throw it at it.
I've not played with them too much myself yet, and given their previous models I'd want to examine the UI fully before making my mind up, but I'm hearing good things about the LG Viewty... Considered that too?
Regards,
Rob.
