I’ve been to several (4 or 5) - can’t go this year as it coincides with another conference, but my boss will be there. We’ve found it to be very useful in terms of strategy, trends, etc., but definitely don’t think you’re going there to learn about tools. If you are a Gartner customer, and can get time for an analyst chat, they’re very useful too.
I should add - the analysts do a very nice job of looking at the BI marketplace over all, and talking about what they see as future diretions. I’d also expect that they’ll address all the mergers/acquisitions over the past year, and talk about how they see that impacting the market and tools in the future.