The marketing for the new .uk wasn't great. Nominet recently sent out an email regarding .uk to everyone who holds a .co.uk explaining the right to the .uk (where applicable) . In 2019 when there will be general availability to all .uk's currently reserved for the .co.uk holders things will get interesting. Domainers will have a big decision to make as it will effectively double the renewal costs.
Over time I can see .uk becoming more popular than .co.uk and this will likely happen after 2019 so there is a good opportunity in 2019 to grab some gems which are not taken up by the .co.uk holder. I am in the UK and I chase both UK ccTLD's and .coms.
.org.uk and .me.uk are seen as lesser extensions in the UK, .org.uk is more charity based, I have secured a city.me.uk domain which was a surprise, but UK domain investors see no value in them. Many end users buying domains have no interest in the .uk , this could be lack of awareness. It will take years for the general public to become fully aware of .uk, to me this is a window of opportunity for domainers. Look at it another way .co.uk could actually be seen as a sub domain to .uk in the future.
I agree with the comment above.uk looks better, of course domainers won't let go of their .co.uk's having probably spent ยฃยฃ on renewals, I think 2019 will offer a real opportunity to domainers and the real advantage being .uk popularity will not have peaked then so domainers holding current .co.uk rights will have some hard decisions to make.