Do you believe it is good value for money for developers to go to training centers to gain new technical skills, or is it better to allow them to learn from books and online resources by themselves?
It's good value first and foremost because it's a break from the normal routine. Go some place else, meet other people, hear lectures about something interesting. Even if a better use for that time would to to just read a book about it.
I like Andy Hunt's take on them: He calls them "sheep dips".
I think they can be helpful, but not sufficient. Hunt recommends SMART objectives:
Specific, Measurable, Achievable, Relevant, Time-boxed.
A one-week course can get you started, but don't stop there.
It depends on the training course, respectively the person who does the training. If they are good at it, it enables them to deliver the big picture faster than a book, which is then still a good reference. It can be far easier to read a book and understand it if somebody explained you before. There is also the motivational issue.
In my personal experience you're better of buying a good book or two on the subject and then just sitting down in front of the computer and working it out yourself. Technical courses tend to be very expensive and you won't really be able to judge the quality of the course until you've paid your money and turned up. A good book or two plus the internet will probably teach you the same except that the only cost will be your time!
I've been on a few and as you'd probably guess, some were great and some very poor.
Where they have been useful, is when you are thrown into a completely new technology area and you want to get a good feel of all it can do, and whether it is likely to be the right solution for you.
They can also be quite inspirational and you can get to talk to other people often in the same boat as yourself - sometimes this is a valuable as the course itself.
I've not found them good for specifics, and you really need to get a word-of-mouth recommendation. The couple I was fortunate enough to go on were given by real experts in the field, and you could ask them anything. Try avoid those who are two pages ahead of you in a book.