I finally got round to unpacking the Hanzo Scanliner/VGA box for my DC a while ago, and thought I'd spray my old DC black and dark grey to match my cab and other systems while I was at it
Could have just bought the SEGA Sports one but where's the fun in that?
My potted review of the Hanzo box is that its kind of awesome. I haven't found any games that it's incompatible with yet (although I have to say I haven't tried a great deal) and the effect is really nice on my arcade cab screen/DELL monitor that I couldn't be bothered to put a bezel around. (I explained to everyone who asked that the space around the screen was for "cooling purposes.")
Thoroughly recommended. You have to get them from the guy that makes them over at the Assembler Games forum, and it takes a few weeks as he's always got orders on, but I'm happy with it. Means I don't need to mess around with cables anymore. Dreamcast on VGA, and emulation PC on DVI. Cable splitter in place to make the speakers work from either the Hanzo or the PC without switching anything - works great!
Edit: Forgot to mention that you can change the height of the scanlines. I've got it on the max setting in that picture, but some will prefer a subtler effect.