Here are some related links from one of the Zimki developers, responding to some of the points I raised here and in conversation at the conference:

http://www.whoot.org/entry/fowa_coverage

http://www.whoot.org/entry/understanding_the_cost_of_a_line_of_code

It's going to be interesting to track Zimki over the next few months. It's not the only tool entering this space. Ning has just released version 2.0 and I'm hearing whispers of at least one more UK entrant on the way...