The price is great on these - there are definitely better quality zip ties out there (I suspect these wouldn't be great for outdoor use), but for semi-permanent cable management, or cables that aren't often disturbed, these work great. At the price, pick up a few hundred & don't worry about it.
I love these small things. They're small enough to not get in the way, but plenty strong. I use these to bundle and organize the wiring in every PC I build. The black color makes it nearly disappear in most black interior cases, but using a colored zip tie to match your PC's color scheme would probably look pretty sharp.
PROS: They cost about 1/3 a penny each and work great