Profile links can be pretty effective, especially in low to moderate competition niches. I would not use them as my only link building method though. Mix in some articles, web 2. blogs, and even some blog commenting as well. Mix it up a bit and you will get better results.
Also all profile links are not created equal, a link from a PR 0 or N/A site is not going to do you as much good as one from a higher PR site.