...is blazingly fast, but I'm so used to Firefox's user interface that I haven't quite had the gumption to make the change permanently, despite both browsers being installed on my machine.

I've loved Firefox for some time. It's very, very good.

Although I'd recommend Safari on a Mac.

I use Chrome - fast and reliable

but prefer Firefox. I just found there were less problems with Chrome.

Funny Simon, I use Chrome as it is super fast but I find it prone to crashing because of an issue with Flash script.
Anyone got any recommendations?

Chrome and Firefox. Since Chrome got extensions I think it's better (and definitely quicker) than Firefox. Either way, once you get used to extensions and the speed, there's no way you'll be going back to ANY version of IE.

You can pick up excellent portable versions of both Firefox and Chrome over at John Haller's venerable PortableApps:

http://portableapps.com/apps/internet/google_chrome_portable

http://portableapps.com/apps/internet/firefox_portable

Personally, I'm a Firefox user. Chrome is faster to load, but I find after it's loaded it is no quicker than Firefox. But, for me, Firefox is the more aesthetically pleasing option.

Chrome - best I've found. Does what it does & does it well.

and I'm using Firefox 3.6.

I use Chrome all the time but it is a bit of a memory hog. Why not just install a few different ones to try, as someone else said, you could try the portable versions but these do tend to take longer to load up and they're not always the full thing, for example, last time I looked, Chrome portable didn't have the F11 facility and I use that all the time, especially when using Google Maps. Also, Chrome doesn't (yet) have a print preview which can be a bit of a pain at times.
It's always a good idea to have a couple of browsers available just in case you want to say, use cookies on one and not the other.

IE8 works fine for me. You'll still need it for a few things in all likelihood, so it's worth making sure you're up to date for security purposes. If you've stuck to IE7, are you updating Windows for all the other patches ? You should.
Firefox has wide use and acceptance, therefore web sites tend to be well tested for it. Make sure it is set to get updates as well (if required). I use that and it's marginally quicker on some web sites.
Chrome is still 'in beta' so I won't touch it for the time being, plus I have considerable privacy concerns about Google in general, no matter how fast it is (perceived to be).
The rest are rats and mice for my money, and have as many or more security challenges according to the IT press I've seen (Opera, Safari on Windows etc). There is no security in obscurity, meaning that using a browser with stuff all market share does not mean the baddies can't target you.

Every time, but especially for things like YouTube. Since Google owns YouTube it makes sense that they would optimise their browser for it. But as everyone as has stated on here already it's superfast compared to all other browsers out there...

Bookshop in Porthmadog is the Fawlty Towers of bookshops. Unhelpful, bonkers staff. Avoid.