Tabbed browsing has been available on Mozilla and other browsers for quite some time.
I know it depends on what you want to use it for but can I suggest all the disgruntled Vista users look at installing some form of linux. I would recommend www.kubuntu.org but there are lots and lots of other distributions. Install is a painless experience and you'll find your PC/Laptop runs far quicker as the OS runs on less memory, leaving more available for your applications.
There are free versions of all the standard applications that you would normally run on Windows - openoffice.org instead of MS Office, Amarok instead of your mp3 player, Firefox instead of IE, KMail instead of your email client, etc, etc. Viruses are (almost) unheard of in linux so no need for anti virus software (although it is available). The one thing linux is not good for is gaming and if that's your thing then you should leave well alone.
There are literally thousands of free applications available for linux - catering for scientists, programmers, ham radio users(!), music producers, maths geeks, etc.
If you're looking for a stable, fast, freely updateable operating system that lets you browse, read mail and news, listen to music, produce documents, spreadsheets, presentations, create databases (CD collection, book collection, recipes, etc), then give linux a go. I did 8 years ago and haven't looked back since.
Give it a go. You can even install it alongside a Windows installation on the same PC and if you don't like it you can revert back to Windows.