Sadly I don't like it. It really is a lame design for a phone and so much of it lacks polish.
Tethering... er, it lacks hardware support but Mango is great. Well, being honest I'm a bit of a 'if it works it works' on this. It doesn't work on my device and that's incredible given that every device (mostly Nokia) I've owned for the past 12 years supports tethering in some form.
Ring/Vibrate... all good here. Maybe you are lucky but personally I like to set my phone to silent and have it beep once then vibrate persistently until answered. Not complicated but I can't do it. The vibrate has it's own setting (ie vibrate once for a reminder) that isn't mine to control.
Keyboard... really good actually. Again, how many other onscreen keyboards have you used. I type at an fairly quick rate and the flashing of the last letter is an annoying distraction (likely to induce fitting in some I'd guess) and the autocorrect poor. I'd say it has improved nicely in Mango, even the portrait mode, but still it's not on a par with Swype or the iPhone and much worse for single hand input.
USB... Zune is great. Don't mind Zune myself but I really would like the option of loading an MP3 onto my phone when at a friend's house without doing a 15 minute install and reboot of their machine to support my device. Why no mass storage mode? Also it does limit the ability to use other nicer music management software than Zune.
Portrait./landscape... all great. Again, seriously. You really think it is fine that your phone choses the orientation for you. This is just lame software implementation. Why is the homescreen only portrait? My phone even has a kickstand to keep it nicely in landscape but yet when I swap between videos I'm dumped into a portrait world with words half split across the top of the screen. It is just a lazy software implementation. I'm sure it boosts performance and speed, but from a user perspective, it is lame.
So what other issues...
- battery life is terrible and some apps really chew it (listen to music for 4 hours and you're out).
- screen lock activates on every screen timeout meaning you have to type a code every few minutes... sadly my corporate email requires the lock on, but lock and screen timeout should be different
- mute doesn't mute the microphone with headphones plugged in... prob more of a bug than design but massively annoying for making conf calls on trains etc.
-email client pulls email 24/7 with no control of 'sleep' times... gotta love those Americans emailing you viagra offers at 3am... luckily your phone wakes you up to tell you, don't miss out :)
- signal indicator is pretty much absent for no reason... there's space there for icons, they just don't show them... weird design choice.
- no receipts for texts or other messages to confirm delivery... an SMS funtion available since er, 1991
- messy (or lovely) social integration doesn't always give you the right number when you try to call... prob a design choice that I could get used to but really some of my friends have 4 or 5 numbers, I know which to call them on at different times, why does my phone assume it can choose the default and always dial just that?
- the pointless search button... just why when you have 7 buttons on a device would you devote one of them to search? It's an 8 gig device and I know what's on there (it is my phone) why would I search it? And if you're just doing a web search, why not just give me my browser?
- multitasking... the most disappointing fail in Mango, this is a pretty lame effort
- app store... laughable selection of crud, no iplayer bunch of other useless crap and not very navigable
I really can go on. I don't doubt than in a couple of years it'll be amazing when the edges are polished but why would anyone give it a couple of years. Sadly my contract has me for 20 more months of this so I guess I'll see...