Well, it won't be a problem on dark colors, but polyurethane has a nasty tendency to turn yellow, which is very apparent on light colors. And it gets darker as it ages. I agree with Galen that MinWax is probably the best buy, in terms of cost and ease of application. Just don't be surprised when you see a color shift. And don't bother with that new water-based polyurethane; it is NOT fuelproof. I found out the hard way

You primed it, eh? Well, sounds like the paint simply was not fuelproof. That, and taking forever to dry, were the two main complaints in the afore-mentioned thread. Either they had a bad batch, or are still getting the formulation right, or who knows? I, for one, won't buy any more for some time. Why take a chance?

Steve