I've used El wire and tape in a number of costumes- I did a write up of my Tron on here: Tron As others have said it isn't very bright. Some colours are much brighter than others though, and to get the best out of it you need to drive it with an appropriate inverter for the length. As others have suggested it may well not be bright enough for your needs Terminating to it is very fiddly, so if you just want a one off project it's easier to buy it pre-terminated in the next length up than the one you need and cut it back rather than terminating yourself. (There are a couple of good tutorials on instructables on this). Normally it's based on a solid core wire, so it holds it's shape but doesn't take flexing very well. For a reliable UK source, I use ELwirecraft. Basic 1m kits with 2AA inverter are pretty cheap- I'd recommend buying one and experimenting.