ugly_bob: you just have to try it out to see really. The interface is wonderfully simple. The spam filter tends to work well (for a web-based email system anyway). I currently have 2739MB of storage, growing each day. There are no annoying large adverts. If you use other email addresses you can set them up with gmail so that you can send and receive them all using gmail.
Two things that really set it apart from pretty much everything else though is the 'conversation' ordering system of emails. Instead of having your email here and a reply as a separate email with "RE:" in the subject, you just click your email and it'll show both at the same time in a 'conversation' sort of style.
Finally, the search is excellent. Far better than anything else in web-based email. And the labelling system is also great. Better than making a load of folders.
damo666: It does work fine in the UK, but you can no longer have the @gmail domain. Instead you get the @googlemail domain. The service itself though is entirely the same.