The .eu may well take off in countries where there is a heavily regulated and or highly priced cctld (.ie in Ireland and .es in Spain etc). Though I think that .uk might be somewhat spoilt for choice and .eu may not make much of an dent in the market in the first year of operation. Remember that .uk is still a very strong brand. And it is cheap enough to compete with .com for the bulk of the advertising business. However since both .co.uk and .com are effectively unregulated, the utilisation (domains active and in use) for both is probably in the region of 60 to 70%.
Regards...jmcc