Arbiters are like sex in late game PvT. Stasis is an awesome spell. As ThingInTheCoat suggested, High templar are also very useful. The Protoss has so many counters for bio and biomech builds it isn't funny. High Templar, Dark Templar, Archons, Reavers, and Dragoons pwn biomech so hard. Attack with Zealots and Dragoons at the same time. He will either unsiege or fight off your Zealots with his Vultures/Goliaths. Sometimes he'll just let them die because Dragoons >>>>>>>> unsieged Tanks. You can slo use Shuttles to drop Zealots on his Tanks as the Tanks splash damage can be detrimental to your opponent.
Don't let him tech freely. You know you haven't been attacking enough if the opponent was able to afford Tanks, Goliaths, and Science Vesels at the same time. The protoss have stronger units than Terran and you should be able to pressure him very well. You should get your first expansion before the Terran does. If the Terran is building an expansion and you haven't started one yet, then you're going to be at a severe disadvantage.
Golaiths shouldn't be too problematic. If your opponent doesn't separate his Tanks out when sieging/his Goliaths, then Disruption Web will be incredibly useful coupled with a Dragoon push. If he doesn't keep everything clumped together then it's not worth getting Corsairs. Get Carriers if you're desperate but they require a lot of micro over cliffs and double pronged attacks to work effectively.
If he gets EMP then you haven't much choice but to spread your units out. You should be doing that anyways. A wide arc of Dragoons is mroe effective than a clump because they'll all be able to attack and they won't be hurt by splash as much. Funding an EMP tech will put him behind economically in the middle game, so you know he won't have as many Tanks and Goliaths if he's getting Science Vessels. Attack in arcs and separate groups to make EMP less effective.
Pure Goon or Blue Goon may work, the Stove even if your opponent doesn't expect it, but it'd generally be best to go with conventional builds. Quick Dragoons with range and then Speed Zealots. High templar are very important and Zealot Bombs with Shuttles are great, especially if he doesn't set up a lot of Missile Turrets. If he goes Goliaths when you aren't teching to much air, then he'll have less Tanks and it'll be easier to win mid field battles. Get Arbiters late game if you can afford it and can micro them decently well as Stasis is awesome and the cloaking will frustrate him.
If he gets Marines, you haven't much to fear. If the Marines are used a lot in his strategy then Archons and some more High Templar and Reavers will do well. That'll cost a lot of gas, but it will slaughter Marines. Biomech is only really viable on maps without gas naturals like Nostalgia. If he attacks with 6 Marines and a Tank and Vulture at the beginning chance are he is NOT going to continue with Marine production unless he produces another Barracks. The Gundam RUsh is quick but mariens lose their viability in most maps after the 5 or 6 minute mark in TvP.
