I have had a twin IR rating for 10 years now and have used it extensively for business purposes.It means you always get there as long as the base is above minima which is usually about 250'.Seldom is the cloud base below this.
To fly IFR you do need three things-an IR,a suitably equipped aircraft with all the kit working,and be in current practice.
I do believe,however,that the IR course is difficult and expensive for PPL's and I wouldn't like to have to do it all again.I did the theory at PPSC over several months on a correspondence course followed by a week of consolidation down in Bournmouth.The practical part was done at Ravenair and was very satisfying and enjoyable to see one's skill level increase to a very high standard.I dare say that the flying carried out during the exam is probably the best and most proffesional one ever achieves.
Anyway,good luck to anyone taking the plunge.