I heard different statements about this.

Officially it's IE7, but some people said it has some old IE6 bugs in it.

Basically, it's probably just another mess that needs to be specifically targeted.

Closer to the IE7 side of things. And while IE7 was an improvement on IE6 it still lacks a large portion of the fun stuff that’s for the past couple of years made smartphone-focused web development a breath of fresh air.