Definitely spam. The comments appear generally positive, but they are often not related to the content of the post, and URL of the commentator is often for some sort of spammish site.
This is a very common practice. The goal of the spammer is to get their URL in your comments section, and the generally positive comment is to fool you into approving it. If you don’t believe me, investigate the URLs that some of these commentators post with.
Akismet is powered by a learning engine, so if it isn’t catching them initially, make sure that you mark them as spam so that it can learn.
