This is an excellent thread for a relative newcomer to PVP SC2. I completed the campaign when I got the game last year but never went into the online stuff. However I finally had an itch which needed scratching and reinstalled the game and gave it a go...
Needless to say I had my arse handed to me - losing all five placement matches and obviously got put into Bronze.
However, taking the builds you've mentioned at the start of this thread, I've managed to up my game (combined with a steep learning curve - I've only just managed to get the hang of fast-build Cloaked Banshee rushes against me - Scan by Orbital command is my new best friend). I'm not sticking religiously to things, as scouting my opposition sometimes shows something of what their strategy is and I have to think on the fly, but they're proving to be very successful - I'm now 42ish wins and 18 in my league.
So, thanks for the tips Dudd, I know they're aimed at getting you into Plat, but they've helped me no end start to understand this rather excellent and exciting e-sport