I had one of these and wore it every day. Interestingly, one day I wore it to work and my co worker said it was a favorite amongst terrorists. He said that Bin Laden, himself, sports one. I thought he was joking, but later that afternoon, I did some quick research online. He was not lying. Apparently, it is a favorite because it is extremely cheap and easily modifiable to set off remote bombs.
It was more likely a favorite because, in addition to being cheap, reliable, and sturdy, it is extremely common and easily available. The same model has been produced since 1989, and millions are produced every year. They're everywhere. It's apparently consistently the #1 top selling watch on Amazon, and the first result for "digital watch".
Possession of an F-91W being used as evidence of being a terrorist trained in bomb-making for purposes of detention at Guantanamo Bay was highlighted as something ridiculous because of how common the watches are. There's ample evidence that al Qaeda bomb-makers were quite fond of the watch, yes. But as prisoners at Guantanamo pointed out, apparently in vain, many guards there wore the same watch. It's just that common.
I'm wearing a W-800H since quite a while, and it feels like an updated F91W. Strap doesn't break, improved lighting, 4 buttons instead of 3 so that you can adjust it in the dark, better date display, and still light, cheap and reliable. Highly recommended.