In my opinion, Fast tech is really valuable in a 4v4 RT game, and the person that is teching actually knows how to do it. I once had this game where me and two partners (both orcs, i was human) where constantly harrasing our enemies, till the techer (NE) finally got to 8 chims and a SH in a good 15 minutes, man did we had fun.
But in 3v3 RT games, i feel safer when im fast teching with undead(best race to tech with) First ziggurat around mines-upgraded to nerubian tower for annoying BM rushes, and produce atleast 5 ghouls and a hero before i go to tier2.
So, its not the teching strategie that blows, its the player that might be the noob. Just dont do it in a 1v1 now, you need tier1 units to keep you alive!
Oh and btw im the rushing type, so i barely go fast tech unless rush fails horribly