Pretty, but nasty stuff. I ended up using Roundup on it and that didn't kill it all. I dug until I was blue in the face. It seems to grow faster than the shovel can dig. Now I've probably made a horrible mistake, but I plowed my flower beds up and I'll bet I have it all over the garden now. I'll never plant it again. :-(
I wouldn't say it creeps as such, in my garden it goes at a dead run LOL. Yes it spreads and the leaves are slightly fleshy. It can also take on a slightly prostrate habit as well as upright, it all depends on the position and situation it is growing in.
A deciding factor is the sap. Go out with a pair of rubber gloves or similar and break a piece, the stem will exude a small amount of milky sap. Don't touch it with your bare skin it even irritates my rough calloused hands!