Depends.
I personally think .co.uk's are great for End-User's, depending on what exactly the domain name is. The domain industry for .co.uk domains for UK business is booming, and if you have the right name, which matches the right industry within the UK, you've got yourself a big profit.
I am not speaking from experiance though, so watch out.
.com is much more known to everybody than .co.uk within the UK, however, it's the big and growing potential businesses that use .co.uk domains, so I see this as a great market for the .co.uk extension.