I fish/float solo quite often also, when I get to go on short notice and can't find a friend. Turnaround is the only real problem, assuming you are capable of running the river you have chosen. With a pontoon you can easily be conservative and carry your boat around anything that you aren't confident running. I would only recommend not going solo if you are inexperienced and want to run a difficult river. Oh, and you won't have anybody to take the pics if you are fortunate enought to catch a fish.
Go for it!