A few queries re: debian vs other.
 

I have been using Ubuntu full time for the past couple of weeks and got it looking / running how I like it. It's nice. Infact - dare I say - I'm finding it more productive than Windows 7, mainly because I can configure the UI so I have a minimum amount of clicks to do anything I like.

Now, I have been messing about with Mint linux in a VM. There are little things that I like better about it. The proprietary menu is nice. But I can still configure the rest how I like it, and it's nice that it's still a Debian variant.

Now a few technical questions, if you please. Firstly, is there any advantage to running a Debian based distribution over any other - say Mandriva or Opensuse? If so, why?

Secondly the font rendering is MUCH nice in Ubuntu 10.10 than in Mint. Can I configure Mint to have the same smoothness to the fonts?

Thankyouverymuchly.

Not really. Every major distribution has it's pros and cons. In the end, it is a personal preference.
Here is some information regarding font rendering in Linux --> http://hints.cross-lfs.org/index.php/Improve_Your_Fonts. Some of that may help you improve fonts in Mint, but simply stating that it is MUCH nicer in Ubuntu rather than specific differences doesn't really help someone point you to the right resources.