[MoMan]

Probably not, as it doesn't add any queries for guests. It depends on whether or not mysql is the bottleneck on your site.

The queries in this mod are relatively light unless a user has hundreds of subscribed threads. It shouldn't add much load, but does add 1 query for all users, and 2 additional queries for users with subscribed threads. On my forum, the non-cached version of this mod added just under 0.01s to the generation time of each page. The memcached version, on the other had, doesn't add anything at all, since most of the time, the queries aren't run.