When it was initially made public, I thought Twitter Bootstrap could prove quite useful and I blogged in that direction. Many months later, I can now see that a lot of people adopted it. They’re recently released a version 2.0, which may well be a response to Zurb foundation. A glance at Github suggests that Twitter Bootstrap is one of the most popular project there.
I don’t have any affiliation with either organisations, but I do like to see something so useful in widespread use. This can only help users and developers, companies that build on such toolkits may be able to optimise their web application interface design costs too.