personal opinion...i have had the avon st s for about 4000 miles now and i think they have another 1000 in them, maybe 1500, and thats pretty average riding, and they are squaring off a fair bit now...and tyre pressures etc have all be checked regularly.
i find them pretty good in the dry, but, and this a BIG but, in the wet they are shocking, horrible, nasty, the manifestation of evil. They grip only a little, anything more thatn pretty upright angles and they slide, apply the brakes a little and they feel like they will let go, any more and they do let go...
like i say this is my experience and opinion, some poelpe find them fine, i however will not be buying again, even though the ffront will probably last another half a rear, i just have no faith.
Will probably be going with z6's or strada's next.
my advice, go with the z6, up to you wether you take it though
andy