A lot of my TvT losses are because I transition to BC/viking too soon or too late... what do use as a benchmark for when to switch? When you reach X bases or...? I usually think "eh... got quite a lot of tanks, should probably get some BCs now" or "holy **** he has BCs i need to throw down starports" by which point it's obviously far too late. It's a pain in the butt how bad they are before they get 3/3 too. IMO BC build time should be reduced by about 5-10%.
These sig things are pretty cool

. I put my US one cos I mainly play that atm (it's easier so I stand a chance of reaching masters lol).