The ZvZ I was talkin' about was Idra vs Sen... I don't think many people would say that is a bad match to watch.
But you also say to watch Day9, who actually said
not to try to create those "cute" armies full of diversity since you end up spending all that time teching them up to proper usefulness rather than getting easier, but still effective units. What am I supposed to do then?
Almost all pro matches are like this that i've seen. Even zerg usually starts lings then makes a backbone of roach/hydra while still using lings to poke, mutas to harass, and specialty units like infestors. Zerg has more economy units that you have to consider to, like queens and overlords and powerdroning. Zerg doesn't have as many combative units.
But what I'm seeing you say is that the majority of their army is still Roach/Hydra. I'm simply stating that in the end, you typically still spam one or two units with a bit of extra added flavor in there. Units can complement each other (like MM) and it's no wonder they make up the majority of the fighting force.
Sometimes, it's simply in your best interest to spam a single unit. Like in a 2v2 yesterday, the opponent was rather good at squelching our expansions (although, I think it was more luck

) and I never had a lot of vespene after I gave 1500 to my friend. I spotted the protoss making void rays (yay, another VR spammer). So since I had plenty of minerals and not a lot of vespene... what did I do? I spammed the hell out of Marines. While they were useless against the Terran's tanks, they fortified my friend's Ultralisks by annihilating the air units while said Ultralisks tore through the base. I could've used vikings, but I doubt I could've built enough to be as effective. The only other unit I probably should've tried to build up more were medivacs to help ferry the marines around (I did have a few).
EDIT:
Hmm I'd watch those GomTV matches (although they're not live at the moment), but apparently you have to pay to watch their video on demand portion

.