identica's useful for Free Software community folks

Meh, the criticism seems threefold:
1) spammers are more prevalent. This is *perhaps* true as a percentage of users. This is very worthy of discussion.
2) There aren't enough users (perhaps in the Boulder, CO, USA area) to get the information you were looking for.
3) identi.ca is chasing twitter's taillights.

The first point is very worthy of discussion; I've noticed this myself.

The second point is a natural consequence of the capitalism instability applied to users on web services. The more users you have, the more users you get, and so on. (in capitalism, it's money instead of users).

The third point is difficult. Clearly, twitter was leading identi.ca when identi.ca was first launched (see Miguel's sole Identi.ca posts).

At this point, however, I think twitter's sole advantage is inertia (the captitalism instability). Identi.ca has features that twitter doesn't (e.g. groups, private servers) and few that Identi.ca doesn't (the only one I can think of is lists, and I'm not sure what value that brings. Identi.ca was first with location services.

So the third point is not clear-cut. The second point is clear; identi.ca isn't nearly as big as twitter and that'll necessarily limit what information is available solely on that site (note, however, that it provides some degree of facebook and twitter integration, although I think it's unidirectional broadcast at this point, but it could be bidirectional).