By painful I mean slow. The vehicle will do it and aside from changing your maintenance schedule to the severe service schedule there should be no ill effects, it won't even be too bad if you are only going a few miles to the launch but if you are traveling on a vacation 100's of miles you will be longing for more power. Also at 5,000 lbs you probably want to look at upgrading the trailer to an electric braking system (if it isn't already figured), that will give you a little more control over surge brakes if you get into trouble.
I personally have always bought vehicles for towing with the theory I want 50% head room for the tow rating, just to be on the safe side. My V8 has somewhere around a 7,000 lbs rating (I think), the trailers I normally tow are around 3,000 to 3,500 lbs, I went with the V8 to have that extra capacity so that I wasn't taxing the vehicle as much.
