Hi,
Started the campaign last Monday. Like Mark CMG, I used the extra encounter on the WotC website, bumping it up to three hobgoblin veterans plus ogre as suggested for 5th level characters. There are five 5th level PCs currently with one more to join a bit later: fighter, barbarian, cleric, druid and rogue 1/sorceror 4. They dealt with the extra encounter easily but the Marauder Attack was much more challenging. I think 5 x 5th level looks about right so far.
Cheers
Richard
PS there's some stuff about the campaign including an account of Session #1 on my livejournal.