I was browsing the web last night and came across WikiSeek. And I have seen an increasing number of vertical search sites using Wikipedia data as the underlying set of source data for what they’re doing. I use Wikipedia fairly often and don’t have any issues with the relatively simple UI. Perhaps I’m missing something – Wikipedia strikes me as pretty easy to use and it’s one of the sites that Google indexes quite frequently.
I do, however, find the theme of Wikipedia-as-seed to be interesting; there is a lot of interesting data in Wikipedia that can be mined and used to address either vertical or popular queries on the web.