You'll have to beat the **** out of it to get it off. Just be patient (very hard) or you'll have it spalling all the edges. Did you know to agitate or vibrate the concrete? If not you MAY have some porosity or "rock pockets". Not too noticeable where you're doing this but if it bothers you, you can "bag & sack" the holes (if smaller) with straight cement and water. Let's see it after you pull the forms...if you dare!
I got the forms out this morning. The wood separated without too much of an issue; the tough part was getting the first corner apart, since I'd built the box sturdily to avoid any kind of cave-in. Luckily I had a long bimetal Sawzall blade which let me shear the first pair of screws and work from there.
In another thread, someone inadvertently flattered me by using the phrase "...on a scale of one to Jack Olsen." This is way off base, since I'm something of a hack when it comes to most of this stuff. A hack with a lot of paint.
Still, on a scale of one to Jack Olsen, my first concrete job rates about a two. I think it's sufficiently overbuilt, structurally. But cosmetically, it looks like the neighbor guy who fixes his sidewalk with some ready mix, pats it down with his hands to smooth it and simply doesn't care that it looks completely different than the rest of the walk.
I should have gotten some concrete tools more elaborate than my cut off piece of 2x4, no doubt (you can see it in the picture). But part of the reason I didn't -- aside from my deeply ingrained cheapness -- is that none of this pour will be visible when the project is done.
I got some cavitation along the sides where the forms were (as Dan predicted). I went over it with a quick hit of vinyl concrete (as Dan suggested). It actually looks worse in this picture than in real life, but here's the ugly snapshot:
Structurally, I would guess that I'm fine. This isn't like a two-post lift where the concrete is stressed in a particular direction and has to act like a beam. The lift I'm putting in works fine attached to nothing at all. Bolting it into the concrete is just for added safety (earthquake? wildly off-center load?), and I've got eight inches of reinforced concrete now sitting underneath it.
That said, if I ever want to put concrete where people can see it, I'll get a truck to deliver it and go out and spring for a bull float, trowels, etc.
Surprisingly, my back keeps feeling better after each step in this process. Maybe I was sitting around too much?
