The changes are evolutionary rather than revolutionary. For example, cut and paste, notes syncing with Mail notes on your computer, Spotlight search throughout the OS.
I consider all these new features 'nice to have'
If you think £6 is worth parting for 'nice to have' rather than 'must need', then go for it! What do you think?
I upgraded mine and it's definitely nicer but then again I have also got an iPhone 3gs as well now so don't use the touch much anymore. The missus has it now and she like the landscape keyboard in notes and email.
If you know where to look you can upgrade it for free, with a jailbreak too. Adds a few features - the shake to shuffle one is quite cool. Looking forward to when they start bringing out some apps that take advantage of the bluetooth