i agree, the new PEN are really good. otherwise you could go for a fixed lens bridge camera like the Panasonic LX-5. you could also get a Leica M8 if thats on your budget. i know, it does not have zoom, but a rangefinder has the fastest reaction speed you can get! problem is: still about 850g with a 50mm lens...
BTW - my Leica R8 with DMR and 80-200 weights almost 2.5kg and is almost every minute with me