A victory, but I feel like I really need advice

Hey all,

Below is a link to a replay of a game I recently just played ZvZ - historically, this has been a really weak match up for me for a number of reasons and I went into the game really nervous.  The only comfort I held as the game loaded was that it was an initial placement game.

Looking back, although I obtained a victory, I attribute it not to my skill but the fact that my opponent made far more mistakes than I did.  I was frequently supply capped, I didn't keep an eye on harvester saturation, my wallet seemed constantly full of thousands of resources (which did come in handy when I massed mutas, but that wasn't my goal... should have used it on tech), I could have expanded a lot more and a lot faster, and above all I needed to scout more.  

My opponent, on the other hand: only expanded once, his muta harass was weak, during my initial z'ling and b'ling attacks on his expansion his primary base harvesters completely stopped harvesting for minutes, he lost a lot of units to b'ling attacks, and his resources were never saturated at any point.  I also feel that had he been more keen to maintain more harvesters, he would have easily had at least two more bases in the south-east. 

I don't really think I deserved a victory in this game... I felt that there were at least two definitive points during which I really felt that he should have won: 1) when he attacked my gold expansion with his roaches - he had unit superiority on the grid and had he maintained a fatter economy he would have had far more units there; 2) when I allowed him to regroup on multiple occasions in his bases, I allowed him a stronger counter to my standing army.   

What I'd really like advice on is unit production - I often find a weakness for me is spamming a unit produce button when I am need of a certain unit (ie... spam for more drones, spam for more overlords, or frantically spam for more roaches or hydras, etc).  How do I maintain a proper balance between workers and military units as the game progresses?  Also, which tech is (besides z'ing speed) is absolutely vital to most Zerg players?

Thanks for the input all!

http://drop.sc/372418