When I still lived in the UK nobody was really doing baby showers. I had a friend who threw one and it's the only one I've ever been to. She's not my friend anymore. The invitation was an email list of very expensive baby items (think Pram, cot, baby monitor, car seat etc) and a demand that I replied within 3 days letting her know which item I would be purchasing.
I replied saying I'd love to go to the shower and that I'd already bought a baby mobile that I would bring along so unfortunately wouldn't be purchasing any of the items on the list. She wasn't happy but accepted this.
The shower involved having to eat baby food and sing nursery rhymes. she counted out her gifts to check that she'd got everything that had been promised, and was very pissed off that some people had just brought along baby grows. Lots of the guests were in and out of the loos doing coke (one lady even took her daughter into the toilets with her, but did have the decency to leave her outside of the cubicle while she took her drugs).
The whole experience from start to finish was absolutely horrific. I didn't speak to my "friend" much after that. I know that most baby showers wouldn't be anything like this but all I remember was a demand to buy an expensive item for her baby and then a really uncomfortable afternoon. It's put me right off!
I stick with the tradition of buying a gift for the baby after they're born. That being said, if a close friend decided to throw a shower I would leave my judgement at the door and go along to be supportive. I think if you're close with someone it's a bit mean not to attend.