The pinch to zoom works as expected, there's a proper undo button, and the only over sensitive touch control is the tap and hold colour picker which gets a bit too helpful if you are drawing dots.
There's a bunch of filters, and effects, and a built in help function.
The only real complaint is that the menu system for picking brushes is a bit too menu-ey, you click the paintbrush, and the the brush type, and then pick the brush, and then click on the size/opacity controls, and then pick your colour... it's a bit long winded.
I briefly used the desktop version of Pixelmator on my mac back when I was doing the weekly webcomic, it loaded quickly, and worked reliably, but didn't work any better than Photoshop so I reverted to that. I can see pixelmator on the ipad is probably much like that, it's fine, but if you are already settled using sketchbook or something else, you are unlikely to switch, unless you are a big fan of brushes, which it has in abundance.
Today's challenge was to draw cords, so I opted for a Geography teacher on a field trip..
Export to png, jpg or psd, save to photos, open in another app etc...
I was slightly concerned when I started the app that it would be a memory hog like Artset, as it warned me I only had 1Gb of memory free on my iPad, but that doesn't seem to have been an issue.