I've tried magnet wire twice, with different results. The first time I really liked them. Most recently I used them in OB for the mid/HF drivers and didn't like them at all. You should know that its relatively stiff wire, almost like a coat hanger, so it tends to kink rather than bend properly. It is also difficult to properly remove the enamel coasting; some use a liquid stripper or solution made from an aspirin, others a pocket knife. It can be very tedious to strip enamel from thin magnet wire.
I second the recommendation for Teflon insulated silver plated wire over copper as a home brew wire. Very detailed highs and much easier to work with than magnet wire. Make sure its silver plating over 100% copper, as many of the cheaper wire now uses an aluminum or copper/aluminum center. For low frequency drivers, I have had luck with 8 or 10 ga solid copper ground wire (bare) and then using something like Techflex cotton braid to insulate each of the paired wires. This stuff has very low resistance and the right capacitance to sound great on the low end. I don't recommend it for the high side however. Use the silver/teflon in that situation.
Almost everyone I know who made their own cables using cat 5/6 (and swore by them) has now shied away from using them, perhaps after the low/cost novelty has passed, the appearance, etc. I haven't personally tried them nor have I had the opportunity to listen to them, so I really cant comment on performance.
