FAA Vs JAR
I've seen loads of people at our club either doing a full IR, or converting - none of the FAA guys have managed it in just 15 hours.
Getting an IMC rating is good if you want to be able to fly to places and know you've got a good chance of getting home agian should the weather deteriorate - but that's all it is - a "get you home rating"
It doesn't give you enough training for prolonged IFR flight, and isn't recognised outside of the UK.
It's a topic of much debate, but having something like the FAA IR rating availbe would probably save some lives - there can't be many PPL's prepared to fork out £10k+ for an IR, and there's nothing inbetween that and an IMC.
As previously mentioned, there is no credit for the hours, but it does make the IR easier when you get round to it.