How bad exactly is the menu to control with a mouse? Is it smooth/fluid or a nightmare like many people seem to think? Anything particularly off-putting about the overall game experience?
Not bad at all. It takes a little bit of getting used to and the UI definitely suffers from a bit of consoleitus but it's not bad. Essentially Tab is your "escape" key or "cancel" key. I had a bit of trouble getting used to the UI for about 10 minutes (which is where most rants are coming from) but quickly got used to it.
The one major problem I saw was that you cannot rebind keys that are passively bound to something else in the UI. For instance I wanted to rebind my F key to "sneak". By doing this I could not Favorite an item in my inventory because "F" is used as the default and you cannot rebind it for setting favorites. The same goes for R (which happens to be the key they make you use to drop items).. YOu cannot rebind that one either. That's the only two I noticed so far.
It's not a nightmare at all...it runs awesome on my PC and the graphics are WAY better than I anticipated. So far I really have nothing bad to say about the game...it's frickin skyrim.
Seriously, this. How is the UI on the PC?
See above.
Hiya, hope you enjoyed your 7ish hours play time

still waiting for my copy to arrive. Anyways a lot of people are complaining about the UI and lack of mouse control of the UI, menu navigation and such. Have you experienced any probs in this regard?
See above.
How does it run? What are your specs? Resolution? Does it ever go below 60?
1920 Res on High/Ultra settings with a GTX 560. It's always at 40+. In one instance when there were MANY NPCs on the screen it probably dropped to 30, but nothing bad.