The kroot rush is so-so. In my experience, basicly what it does is just stalling, until the Tau can tech up and finally move in for the kill (The Patient Hunter I guess is they way of the Kroot after all )
I think vs SM Tier 1, Tau wins over SM, no chance given to SM at all. With Tau Commander and Fire Warriors and the right micro, Tau owns FC + Tacs. However it quickly changes, when ASM enters the building. Unless you have more FW squads than he has ASM squads, given that your micro is equal, he will win. I don't know what Tau has to do to win over ASM? I tried out Kroot but they wouldn't do much damage, however they kinda clogged the ASM up so I could outmicro him.