Hi all, thought I'd get myself started on here by chucking my tuppence worth in...
Can't really comment on Z tyres at the moment, but I would say that brand marketing doesn't help grip one bit! My Celica came with Pirelli PZero Asymmetricos which were apalling on anything other than a warm dry road (when they were, admittedly, pretty good). Even contacted Pirelli Tech about it and they suggested using Direzionales on the front to clear water and Asymmetricos on the back, but I couldn't get them in the right size.
Took a mates advice and swapped them for Yokohamas, first A539s (decidedly average) and then Parada Spec-IIs, and ended up with Toyo T1-Rs. Best gripping were the Paradas, but they caused a really dodgy resonance at 40/80mph which sounded like all of my bearings were catastrophically failing, then probably the Toyos. They have a soft compound (don't last as long) and rounder edges so give a more progressive break-away which gives you more confidence, particularly in the wet. Obviously it was a different car, but the principles still apply. I'd definitely rate them over the PZeros regardless of brand prestige. I know a few Lotus owners and all have ditched the Pirellis in favour of Yokos.
Getting my Z tomorrow and it's on Falkens so I'll let you know about those...
Also, Vredstein do dedicated performance winter tyres (often seen on bizarre concept cars at motor shows). Anyone tried those? Not sure what the warm weather penalty might be - possibly huge wear rates - but if you've got two sets of wheels, it could be worth a try for the cold months.