Initial impressions:
Build: Simply outstanding! This is easily the best built phone I've ever owned. Matte black body looks very good. It does not feel unduly heavy to me, rather it feels as if it's been made with some very high quality materials. It's about as large as the Samsung Galaxy S3, but much easier to hold due to its slightly curved back. The ceramic buttons, & Zirconium housing for the camera all look very nice & adds to its high end look. Nokia probably could've cut about a centimetre at the bottom. The extra space between the 3 touch buttons & the bottom edge could've been avoided.
Screen: Bright and happy! Extremely fluid touch screen, easily matching the best out there. The UI is very nice, & I'm happy with the degree of customisation it offers.
Setup: It helped that I had already set my account & contacts list up in outlook.com. I simply signed in & everything came into my phone automatically. Once I set my Facebook, LinkedIn & Twitter accounts, all the contacts got automatically consolidated (although I had to link some manually). The one mistake I did was, I imported my gmail's address book into outlook, & also synced my gmail account to my phone. This has resulted in unnecessary duplicates (even though they're linked under one name).
Call quality: An absolute revelation after the terrible HTC Sensation. Shows a good network, & call quality is clear.
Other features: Voice commands (like Siri) seems to work well. It has understood my commands the first time so far. There's a dedicated camera button, which surprisingly is a very useful feature. I don't have to look for the camera app. The camera instantly starts when I press the button. The music player has a graphic equaliser.
Negatives encountered so far:
1) The wifi network switches itself off when the phone goes to sleep, although it connects quickly when you go to home screen.
2) No common notification area as yet, although I'm told it will common the next update. The live tiles help here.
3) Alarm is a separate app & not integrated within the clock.
I haven't checked the App Store properly yet. I have downloaded some basic apps like Facebook, Twitter, Skype etc. & have downloaded UK map onto Nokia drive.
I haven't noticed any bugs as yet.