I've got Toyo Celsius XL (stiffer) all season on my Scooby Forester Turbo which are the standard performance version and they cope better in the summer than the OEM tyres and were fantastic last winter, but they are wearing worryingly fast, probably twice the rate of a summer only tyre. Also any mixed tread pattern is going to be a little noisier. The Proxes 4 Plus are the High Performance version, I'm guessing they will be excellent but will presumably wear a little quickly as well.
I've got Michellin CrossClimate all seasons on another car whilst they are considerably more expensive, wear better and 'feel' more like a summer tyre whilst offering even better winter performance I wouldn't want them on my Z4 for spirited driving, I've a feeling they would lose-it on hot high speed road cornering, be too soft in the sidewall and probably scrub the corners off in no time.
Be interesting to see how Proxes 4 Plus work out 8)
