I know the guys from techtalk personally and they're friendly people (one of them left for Intentional software though). Their o/r mapper isn't that bad, though they lack a set of features which I think is essential for data-access, like authorization, auditing, REAL linq implementation (although their linq provider is quite OK compared to the rest of the o/r mappers who claim 'linq support'. Not as good as ours though ), and a proper designer. They use dynamic proxy for dealing with POCO classes which is a mixed bag: it could be great but has serious side-effects in for example distributed scenarios.
From second hand sources I heard it's also not quite that fast, but I haven't tested that myself.
I also agree that messing with xml files is not the way to go. You can get very far with an xml file with domains the size of northwind, but when you have hundreds of entities or even more, it's starting to become really really complex. With all the work done on llblgen v3's designer in the past 10 months or so, I learned that model-first is really only doable in a designer which helps you along the way and tells you that this is wrong and that is ok and do this to correct that so you don't lose any time.