So QGIS Server didn't win the performance shootout at FOSS4G2011...sniff. However there is no need to be alarmed - if you hide QGIS Server behind a tilecache you don't need to let your users wait around for their maps to render. I hadn't tried QGIS Server with TileCache and was curious to know how well it would work. I was a bit worried about label clipping and duplication as we don't yet have any directives you can pass to the server to make it aware that we are tiling. I used TileCache's metatiling options:
[advanced_iframe securitykey="da39a3ee5e6b4b0d3255bfef95601890afd80709" src="http://utno.linfiniti.com/tilecache.html" height="300"]
Note that the cache is not pre-seeded, so if you are the first to visit an AOI of interest, it will take a little longer to render.