Absolutely!

I usually fish a wet fly upstream with short drifts. If I can't see the line as I'm casting, I'll miss the first half of the drift before I can find it and make sure there's no excess slack. Plus, the subtlest twitch or hesitation of the line is often the only indication of a strike. I have to be able to see the line very clearly. Being able to see the slightest twitch more than offsets (by a large measure) any thought of a bright line scaring the fish. Besides, I don't think it scares the fish.