I've been using POP for a long time and it's evolved a lot from when it first started. I wanted to offer this story of mine before you consider using UI Stencils again.
I had a slight run in with UI Stencils, after having bought a number of items off them in the past. I ordered pens from them which, when they didn't arrive after a month, I contacted them, asking if maybe they could resend them as they must clearly be lost in the post (they provided me with a shipped date shortly after I purchased). The return correspondance was along the lines of "Maybe wait a bit longer, see if they turn up." My communications with them quickly broke down as I went from a patiently waiting customer to an irate customer. My irritation came solely from my communication with them and, where if it had been handled correctly, I'd have been happy to continue waiting, their obvious lack of interest in my (minor in my eyes) problem, escalated my anger. Eventually, they reluctantly resent the pens. The originals never appeared.
Later I heard they released ProtoSketch and was shocked when I installed it to find that it was identical in almost every way to POP. The UI was different but the implementation was the same. I put it to WooMoo Inc (the company that make POP) on Twitter that this seemed very similar. They replied to say that they were as surprised as the rest of us, especially since UI Stencils had been an "early beta tester of POP" for them. UI Stencils had given no indication to WooMoo that they intended on releasing an app, let alone that they were even working on one. It is the most blatantly obvious IP theft I've seen in years. I've stung UI Stencils on twitter whenever I've had the opportunity, but they never rise to the accusation. Their lack of response stinks more of their smugness, than of their concern. I know this is my projection, but there's plenty of water under that bridge to make me feel that way. Still, I am not WooMoo, so they are going to have to deal with it in whatever way they see fit. The only outcome is that this news, coupled with my personal experience of dealing with UI Stencils, means that I will never support them again, and discourage others from supporting them at every possible opportunity. They might make clever products, but in reality, they care little about the User. Ironic, eh?
If anyone would like documented proof of these conversations and tweets, I will happily provide them.