If you're in dense traffic or high speed traffic, the seizure-inducing flash pattern may make sense, and people are not going to be close to your light while looking at it head-on. On the other hand, if you're going to be on a bike or pedestrian path, you'll be better off with a gentler pattern or no flashing. Cygolite headlights have a mode called steady-flash which has a constant beam at medium intensity and a flash (at about one per second) on high. This is not terribly annoying to face, as I've seen riders with this while on the bike path. The bike path is narrow, so I'm looking at oncoming traffic at a very acute angle. The aggressive mode is annoying and unnecessary.

I do most of my rides on my commuter bike which has dynamo powered lights. The headlight doesn't flash at all. This is OK for me, since I'm mostly on the bike path, and I don't spend a lot of time where I have to grab people's attentions aggressively. Other people have different needs.