I have recently put commentluv on my blog after having seen it on so many other sites. If I leave comments on other sites does the link left act as a dofollow link or simply another chance for people to see my site?
Yes, dofollow is effective to link building, but now many blog have commentluv but not dofollow. The comment still nofollow
You can check up the dofollow link using nodofollow firefox plugins: https://addons.mozilla.org/en-US/firefox/addon/5687 I'm not really sure about the backlink but it really help on generate traffics if our post's title is catching eye's reader.
If you are good at writing enticing titles, commenting on commentluv blogs can get you a lot of visitors.
Both they are.. if you left a link to a site that is a do follow you can generate traffic from it and that is for sure.