I agree with the EU on this one. Competition is a good thing. Microsoft are able to gain a big market share on browsers simply because they own the most market share in OSes (I think this is a bad thing)
So I think this browser choice thing is a step in the right direction. The point is to stop any browser vendor getting power over the web. When that happens you get them trying to push things like ActiveX, Dart and NaCl. Weather or not you like those things is not the point though. But the idea of having multiple browsers all with a chunk of the market share, they can stop the bad ideas from catching on (web developers tend to not like writing websites that only work in one web browser)
The EU want a world where no single company has control over OSes or browsers
This browser choice thing was thought up back when IE had a 95% market share though. Its a bit dated but I think its still necessary as it gives all browsers a chance of gaining a decent market share without needing deep pockets (Firefox proves you don't need deep pockets to make a good browser)
If Chromes market share ever goes above 80% I bet the EU will start putting some rules on Google. But I don't think that will ever happen though
They would also love to take Microsoft to court over Windows but Macs are too expensive and there aren't many companies supporting Linux at the moment so they can't. But they will if they get the chance. Imagine a world where Microsoft has to work to sell copies of Windows!