Thanks for making such a fantastic suite of libraries and not neutering them with a GNU license.
After using Poco for a while, I've started to do the unthinkable: stop using Boost. Boost is a great set of libraries, but let's face it, unless you happen to be a member of the C++ standards committee, the code is nearly incomprehensible, and if you use it a lot your own code will quickly suffer the same fate. Poco has been a real pleasure to work with from a user perspective. So now if I need some functionality, and that functionality is exposed by Poco, I will use Poco almost every time. The only Boost library I really use any more is Spirit for those cases where regular expressions just don't cut it.
I've also mostly eliminated another monstrosity (ACE) from most of my networking projects, thanks to Poco Reactor.
I HAVE found some things that are not quite as mature as I'd like, particularly when it comes to the stream/buffer classes, but the code is so clean that making the changes that I need is easy as can be. The few times I tried to make changes to Boost libraries, I wanted to end it all. I'm going to look into making some contributions of the changes and additions that I've made.