First a full disclosure, I run a chain of Adobe Authorized ColdFusion training centers.
Whether or not classroom based training is worth it for you, is based on a few things. If you find self-study to be effective, it is certainly the least expensive option. There's nothing magical about attending a hands-on class, or attending a conference. I find it's a way to make certain you get some learning under your belt. For a lot of people self-study can be hit-or-miss and it's difficult to stay consistent. The other thing about live training like classes and conferences is that they tend to be a lot more fun for most people, and training sticks best when it's fun. Sorting through the ColdFusion chaff on teh web to find the wheat can also be difficult.
Most people who do attend instructor-led classes or conferences, though, do have employer sponsorship.
Hope that's useful.
IMHO training and conferences serve a very different purpose.
Training is useful for developing your skills. Particularly when you are in the early stages of learning a new product / language. For many people getting started with something new is pretty daunting: installing a development environment, buildin a "Hello World", then switching to a real world example etc. Once people get past the initial hurdles the ROI of training decreases. Training is not going to help anybody moving from a "comfortable with" to a "guru" level.
Where training is particularly useful is when a team has to get started with a new technology while under a project deadline. Getting some trainer on-site to run the team through a training for a week and perhaps do a day of consultancy on the architecture for the project will easily shorten the cycle for that project by a month.
IMHO conferences and user groups are mostly for networking. The ROI very much depends on what you do exactly and what you want to achieve. Typically conferences are a geat way to get to know people. For us it typically is a way to meet developers to see if we would want to subcontract work to them. For others it is a way to meet companies like ours they might want to work for.
The technical content and skills learned at conferences are usually not the primary reason to go. Though especially if you are in a full-time position and have to little time to keep up with everything, getting a few days to see everything that is going on is a good way to get the priorities for your self-study clear.
And for the purpose of disclosure, I am CTO at Prisma IT where we split our time between development, cnsultancy and training for ColdFusion, Flex and LiveCycle ES.
Those are some great points Jochem. I agree that structured training is not going to take anyone to the guru level. It can introduce a new concept to exerpienced developes though, say LiveCycle to experienced Flex developers for example, or curves based color correction to experienced Photoshop users.
The other factor of both classes and conferences is the enthusiasm factor. When I want to learn a new technology, I like to go to a class or conference because it actually gets me more excited about the technology and gives me the boost in motivation I need to get past the initial hurdles.