Great result for UKIP, obviously, but the rejoicing slightly tempered by disgust at two seats going to the Greens (again).
It can't be said that the UKIP vote was a fluke, but though they may keep many of the votes in a general election, those votes won't do them as much good. The drop in turnout from 2004 to 2009 was close to the total UKIP vote. Even supporters of the EU now realise that it doesn't make any difference who sits in the European Parliament. The only thing at stake in a Euro election is the salary and expenses package. This is immensely valuable to a small party, so supporters of small parties are motivated to vote. Also there's a kind of poetry in electing anti-EU MEPs, so UKIP do much better than other small parties.
As an aside, I was amused by the delay in counting the results in order to wait for other member states who voted at the weekend. Pretending that there was a single Europe-wide election simply drew attention to the fact that there wasn't. The BBC's web coverage was particularly annoying, as results in other countries were reported only in terms of the EP "groups" - so for instance if you look at the Ireland results, you're left trying to guess which parties won seats - "Left" got two and "Socialists" got two - what are they (I think its Labour and Sinn Fein, but I don't know which are which). "Liberal" gained three and "UEN" lost four - quite a shakeup there! I suspect that's Fianna Fail changing groups, but if I want to know for sure I have to look somewhere other than the BBC.
Because elections happen so rarely, it takes many years for people to learn how to use them. It wasn't until the 1980s or even 90s that tactical voting really got going, and voters are still learning that in EU elections, they can vote for whoever they want. The tactical voting will really make itself felt in the next general election, and any prediction based on "swing" will be completely off, as the measured swing will go to Conservatives or Lib Dems depending on which one is more likely to beat Labour.