MOTD/Server List Updated
http://www.mediafaction.co.uk/L4DServer/motd.htm
I would recommend to anyone wanting a full-on, balls to the wall, damn near impossible challenge to download 'Heaven Can Wait' map (download link provided in the motd page above) and put it on expert. Kudos to Sh4rk for spotting the map.
Link, Kearney, Sh4rk and myself tried this on Saturday as an expert campaign. We started at about 5pm and we had to give up at 7:30 only getting to the start of the 4th level!
Not only are the hordes more numerous, there are instances of several witches throughout the levels and sometimes more than one tank. The level designs themselves are very well done, the level where you walk through a dense wooded area to a cemetary are particularly nasty as you can't see more than a few feet infront of you and if you get boomered in there, you're toast.
The way the weapons are placed is also very clever, you'll start out with only dual pistols, followed by a single pump-action shotty for the biggest part of the first level and on expert you'll have to be very careful indeed!
I rated it 4/5 as there are still a few bugs and the finale could have been a little better. One bug in particular to watch out for (not that you can do a lot about it) is when you're in the sewer on the 2nd level, if a horde mini-event triggers then in most cases your L4D instance will crash out to the desktop. The best tactic we found was to send two players through first to the end of the tunnel, followed by the remaining players. That way it's less likely that you'll all crash to the desktop and be able to rejoin the game still in progress, otherwise a restart will be necessary.