I’ll be honest: one of the things I like best about Site 3 coLaboratory is the stupendously awesome logo, which I’ve unilaterally decided to name “Trixie.” So, it is with no small measure of glee that I link to the pre-order for the first t-shirts featuring the logo, which are being sold as a fundraiser. I mean, just look at that design. 
While I’m on the subject, and because more than one person has ended up on this blog because they were searching for it, I’d like to say a word or two comparing Site 3 to Hacklab.to. (I’m not really going to say much about InterAccess, because I don’t really have experience there.)
I love Hacklab, I love being a member, and I consider myself a regular participant there. As great as it is, though, its central location means that it is housed in a very small space. There simply isn’t room for large-scale tools and equipment, and there’s no real desire to move to a different space. Related is the issue of teaching space: course enrolment is limited by the room size, and if something is being taught then no-one else can really use the space. (From what I’ve seen, InterAccess has plenty of space, but it’s not really configured for heavy machinery, either; I might be totally wrong about this, though.)
Site 3 has different goals, and so will have a different type of space: the plan is for Site 3 to be a space where people can do metal-work and flame effects, amongst other things; there’s also plans to have dedicated classroom space, which will allow workshops to run without preventing others from working on projects. Of course, in order to get more space, it will almost certainly be a little more out-of-the-way than Hacklab. It’s a trade-off.
Basically, I think Hacklab is ideally configured for programming and small-scale tinkering, whereas Site 3 is going to be more about larger-scale sculpture/installations and teaching. That, in a nutshell, is my opinion on the difference between the two spaces, and I’m looking forward to participating in both!