I don't have the D55 with flash yet.. I have two IR cams. Went IR to keep from people seeing a flash from the road. I am getting one of these next, but if you can get it for $89 I guarantee you won't be disappointed with the picture quality. Bass Pro had the IR on sale cheaper than the flash a while back so I bought those. The medium quality pic settings are just fine and I'd recommend getting the software upgrade to get the faster times between pics. I think 1 minute comes standard but there is a patch that will give you down to 15 seconds. Also the 3 shot burst setting is great. Wake up and trigger speed is really fast.
Both of my cams are still in the high 60% for battery life. I'm not really expecting to change them until early to mid summer now the way it's looking.