It was very much inspired by the enthusiasm for new gTLDs that never worked out. Nominet bungled the who introduction of it and it just hasn't been as successful as the .co.uk in terms of registrations and usage. Many of the .uk websites simply redirect to their registrant's .co.uk websites.
Yes, people haven't shifted from .co.uk when it comes to usage and sales. The big sales happen in .co.uk and not .uk still. I'd love it not to be the case, trust me, but it looks like .co.uk is here to stay.
You do see a fair amount of usage of .UK on a local business level...(side of a van, contact mostly) But these domains have been registered at basic cost as purely a contact, basic web page.
No reasonably sized business is going to throw good money at purely a dot UK presence. despite what Nominet would try to make you believe. Far too much bleed to the .co.uk.
check out 'Domainlore.co.uk' for current selling/bidding prices for both .co.uk and .uk. The only sales in UK over a £100 are for strong single words or towns etc.
The only advantage or should I say leverage, is if you own both the .co.uk and .uk. Most .co.uk buyers would like the UK (for free) if your offering it as a package. otherwise they'll stick with the .CO. UK
Yes I agree darb, It's not worth paying the UK renewal prices in the hope of a sale. The vast majority of dot UK domains are either held by the corresponding .co.uk owner or by Domainers. The co.uk owners are happy to use them as a second-string redirect and the Domainers are hoping to see the .co.uk drop. Surprisingly I have seen most of my dot UK drops picked-up immediately But, my investigations show each pick-up is by a domainer with wishful thinking..
There is very little leverage for the .uk as a stand-alone.
The domainlore website is great for showing you what doesn't sell. Domains that would be snapped-up in .co.uk