Well, you have caught my delinquency. I worked with this some months ago, and was just finally pushed into reviewing by your message on my admin panel! I don’t have the details, but I can give you a general overview.
The major issue for me was false positives. I had a number of regular commenters, on my personal blog especially, who had difficulty with posting comments. When I removed WP-SpamShield those problems went away. I’ve been using Akismet successfully on the impacted sites (2 sites), but using WP-SpamShield on all others, the majority of which were more web sites than blogs.
At this distance I lack the sort of data, such as what browser those users were using, and even which version of WP-SpamShield it was at the time. If you would prefer this review deleted I would have no problem with that.
