Well I have a couple hours into Okami now, and here are my thoughts on the controls (Nothing to say about the core game except it is GREAT):
I'll admit early on in the game there was one scene where you had to slash some dummies, and I had to repeat it OVER AND OVER again, it got tedious. All I needed to draw was a simple line in the right spot and that was it, well after trial and error I finally beat it but with the thought "Hey maybe line drawing isn't that good, even if the rest of the brush controls are virtually spot on). Well I soon learned that the reason why I was screwing up is that in addition to holding Z (This helps to draw a straight line) you don't need to rush things. I was playing the game like Dragon Quest Swords where I thought I had to do quick slices, though all it really requires is a line in the right place and it doesn't matter how long it takes you to put it in, as long as you stay in paint mode. When you release paintmode the action commences. Now that I've developed that simple strategy (Though it didn't seem so simple before hand!) my lines register near 100% of the time when I'm holding Z.
So what do I think of the controls overall? The waggle is ok for main attacks, but the brush controls of the Wii controller rock once you get the hang of things. I cannot imagine drawing all that stuff with an analog stick. Looks to me that some reviewers didn't take the time to learn the controls, or may not have even known about the Z trigger straight line help.