>Rarely have I seen interesting discussion happen in the comments of a personal blog.
I disagree with this and even more so if we are talking about programming blogs. A lot of interesting discussions and rebuttals happen in the comment sections.
Regarding outsourcing search to a dedicated search engine, its a mixed bag. 99% of the users don't even know about the `site:` and `filetype:` stuff. You also have the option of embedding Google site search but the first four results are ads which isn't very ideal. Wordpress search is decent out of the box but if you want something advanced, it has some nice plugins that allow advanced searching with fuzzy matches.