Well, I've played a LOT of Starcraft 2 over the past 3 weeks, and what do you know? I got promoted to Platinum in Season 4. Yay me!
Now I have a whole new set of problems. First, I'm losing a lot more. No one likes losing. Most of all, I'm losing to "early air strategies" against Protoss and Terran. But WHY am I losing? I'm losing because:
I'M NOT SCOUTING PROPERLY!
What does this mean? It means that I scout too late, don't scout BOTH the front AND the main base itself, and I don't Baneling Bust against tech builds, which should be a tool in my arsenal.
Scouting the front is important because it will tell you things like army composition, and it will tell you about impending early-aggression builds such as Hellions. It will also tell you whether your own early aggression will pay off, such as "how many bunkers or cannons or spines did he build?". I suggest scouting the front at the 4, 5, 7 and 10 minute marks, at minimum.
As a Zerg, you should be floating an Overlord into your opponent's main base at about the 30 supply mark, which should give you an idea about his tech. If you're smart about the direction your Overlord comes from, he should see SOMETHING before being shot down.
Taking Xel'Naga towers is another important one. I lost a game because I Roach-Rushed RIGHT BY A TOWER I didn't hold, giving my opponent the time to build Bunkers and Marauders, and then crush me with Banshee harass and a follow-up Marine-Tank push. /facepalm
So... while Macro got me to Platinum, it's not going to get me into Diamond unless I get smarter about scouting.