Yes, I did, and I thoroughly enjoy having them in the game. Regardless of what people may say about the AI (and I agree with some of it) having different AI civilisations leads to different games, and playing some of them is fun. I enjoy the diversity of lots of different civilisations in the game, and I enjoy using lots of different ones as well. So far I've not regretted any of the civs I've bought.
As for price, I'm currently in a situation where I'm having to live on pennies, due mostly to the fact that when I did have money I'd spend it on beer and takeaways (can you tell I'm a student
) which, for one sitting was generally more expensive than buying a single DLC civ. Looking at it, I'd much rather pay for something that's going to give me a long-time satisfaction than a takeaway that's gone in half an hour, and digested by morning. At the very least I got longer play-time and enjoyment out of the Spanish than I ever got out of a pizza, so I really don't see what people are complaining about on the price front, unless people are so stingy all of a sudden.
If you're still in the air about it, then I'd advise, next time you're buying an extravagant meal, eating out for no reason or getting a takeaway, ask yourself how much you really, really want that meal, compared to how much fun you might get out of a DLC. If you'd still prefer the meal, that's fine, but then that's not a price issue. If you think you'd like to try the civ and it turns out badly, you've barely lost anything that you wouldn't have lost anyway, after a day.