I simply like the fact that the British Prime Minister must come onto the floor of Parliament and engage in debate with the opposition, without scripts or teleprompters. I find it to be a much more engaging way of debating and making policy than what we do, which is write remarks ahead of time, and make them to the cameras on C-Span while almost everyone else in the chamber is absent or outside. It's a facade whereas the British at least have some spirited and real discussion.
From the point of view of an American, it is probably interesting/strange that more than one party can share power in a coalition government like the one that they have now. We can't really imagine having that in the US.
I suppose it is also interesting that they do not actually elect their prime minister. The vast majority of the country had no chance to vote for or against David Cameron. They just elect their MP and whichever party (more or less) gets the most MPs gets to decide who the PM is.