We have a bunch of guys running LIPOs at our track and not one has caught fire. I have seen NIMH melt chassis already though.
I have been using the same LIPO battery in my 4WD for well over a half year already and not one problem. And I have had some pretty horrific crashes too. This is a maxamps battery, so it isn't even hard cased. Not only that, it doesn't fit in my battery tray properly so it even came out once and was rubbing against my tire. The battery is pretty light but you can add weight to counter-act that. This battery is battle worn and still shines like it did when I bought it. I have only used the LIPO with novak GTB and 5.5r and the mamba 5700kv and now the mamba 7700kv. I use the same battery all day, charging between heats for up to 3 heats and 1 main and practice! I couldn't do that with my NIMH, I'd have to rotate between at least 3 packs.
LIPOs are up to the challenge and it is just a matter of a year or two before ROAR legalizes it because it is so mainstream and safe.