It's not too bad and you shouldn't have to worry about maximizing your Brewmaster performance if you aren't doing progression raiding. Here's a simple priority you can use for 'ok' tanking, which is probably fine for heroic 5 mans:
Purifying Brew if stagger is yellow or higher (1 chi)
Guard (2 chi + 30s cooldown)
Keg Smash->Breath of Fire when it's up (treat them like a combo, and only use them together--skip BoF if the target is immune to Dizzying Haze)
Blackout Kick (2 chi)
Expel Harm if > 40 energy
Jab (single target) or Spinning Crane Kick (aoe) if > 40 energy
Most of the time you will just be rotating between tiger palm, jab and blackout kick, since everything else has a cooldown.
I need to setup my weakauras to remind me to guard, I forget it OFTEN, but my healers still love healing me ^__^
My weakauras shows me when guard is cooling down, warns me when guard is off cooldown but i don't have enough Chi, and makes a specific alarm noise when Gaurd is off cooldown and I do have Chi. I'm still tweeking it though.
without going into too much detail.... it is AWESOME, ENGAGING, AND FUN! it is the most enjoyable experience i have had as a tank.
I was going to name my Monk 'Kungfungus' until I changed my mind at the last second. SOOOOOOO glad I did. Every Monk and his grandma seem to have "Kung" in their names.
As for Monk tanking, I like it. I think it's more fun than my DK and Pally tanking, about on par with my Warrior tank and a little less fun than my Druid tank. And yes, I do love tanking and I have end game raided on every tank except Monk so far.
"It's not what we don't know that gets us into trouble; it's what we know for sure that just ain't so." ~Mark Twain
"The time you enjoy wasting is not wasted time"