I think is still useful, of course you choose the finest forum, > PR4 and fit with your passion, its much easier to follow the topic, not just leave your mark
It's a two edged sword to ban signatures. It is a good way to create the incentive to produce good content. But you'd have to concede that a lot of content produced solely for this purpose is of questionable quality. It is said that it becomes to prevalent (spammy commentary) that it greatly outranks legitimate content. I wouldn't think of putting in a signature to my website as it isn't up yet and not relevant to this forum. I think if you do you discredit yourself and also the integrity of the forum.
if you can find a relevant forum it is always a good back up option but i tend to prefer blog posting