Yes. Have done so for the last 3/4 years. Never let it get to big, and keep it to about 25 / 30 sites. I get domains that have juice, and then do a few things to try and keep the juice, and build new sites around them. Nothing to fancy, as it is just part of a network, but also nothing spammy.
Results? Indexing once linked from a few of the sites is a matter of hours. for long tail keywords getting them to page one is pretty simple, and I do have success with one word keywords to. Although sometimes need to use other methods as well as the link network.
I try to avoid letting people post onto them if at all possible. I have done a few times, but try to keep it to an absolute minimum.