Taxes are done and in, and let me tell you: having an accountant do them is a godsend!
It wasn't the best case scenario for rebate/payments, but I did learn one very important thing:
If you're working as a sole-proprietor and the agency you're going through gives you a T4 at the end of the year, ASK QUESTIONS. Turns out that organizations that claim to have to with-hold EI or CPP don't...at least they shouldn't be for fully independant workers....and that's what happened with one gig I did for a local head-hunting firm.
As a result, that amount had to be recorded as taxable income (there's a T4...T4 = you worked somewhere).
I'm curious to see the actual print-outs to see how it was all calculated, but so far my first 6 months has had some good lessons learned, and I didn't take too much of a hit...so we'll see what shakes!