After being berated by Lozza for running 30:1, I've gone to 20:1, and am a convert.
Haven't had a blow-up since, and when you pull engines apart, everything is new and pretty (ignoring stuff that's sucked dirt, or whatever...).
Apparently they're supposed to make more power at the richer fuel:oil ratios, but I can't say that I've noticed.
Tyres. On a recomendation from this forum, I've fitted S12s to the front of a couple of my bikes and have been happy with them.
But more recently, I've ridden with other tyres that are in decent condition, and I'm not really sure I can feel the difference.
Interestingly, I replaced the almost-new S12 on the front of my (modern) Husky enduro bike with the newer Michelin hard-terrain tyre (AC10?), and even in the loose stuff, I feel more comfortable on the hard-terrain tyre.