Con, you don't say when you are going. Caribou is a very nice lake, pretty and with good fishing. It is also an easy daytrip to Johnson Falls which are definitely worth it. If you could get the site on Little Caribou you will be lucky but good sites on Caribou as well.
The portage from Clearwater to Caribou is a challenge but nothing terrible. There are a couple turnoffs that you want to get right, other than that just plan on a long walk through the woods.
Here is a trip report from the area which shows some Caribou Lake scenery as well as Johnson Falls, and info on how we did not make the right turns on the portage.
Clearwater, Caribou and beyond Think you will enjoy it.