Tried it on L4D1. Was a bit laggy which took some of the fun out, but that's not the DLC's fault. The last stage was pretty exciting though, and freaking out. The tanks got on the bridge and beat the crap out of poor Kunai, I had to jump off with some pills and restart the generator. By the time I got to it and restarted it, the other three had died. The "Supreme Sacrifice" ended up being the sole survivor (I was Francis).
Very fun, the first 2 maps were great, though a few parts just screamed "UNFAIR VERSUS" but whatever...
the only thing i hated was sacrificing myself and watching as i simly drop to the ground...they should have made a small cutscene where you see a tank/the tanks closing in on the sacrifice as they try desperately to gun them off.
also: i think its hilarious when my camera zoomed out of Zoey (me) laying on the ground to see 2 tanks standing on the raising bridge XD sacrifice to save them my ass