I really enjoyed working with the P+S adaptor, and would recommend it - but only if you plan for the light loss you will get with it (just shy of 2 stops) and also tight focusing. Plus it matched the look we wanted - and I'm a believer that the adapter is just a tool to get a "look" rather than it being a hd "film match" or anything.
We had a problem or two with matching the adapters (the feature was a two cam shoot) - basically we had an adapter malfunction midway through shooting, and had to get a new one on there - when we did, it had a noticeable change on the image - added an magenta-esque element that wasnt there with the previous one. We made a few in-camera adjustments, but because this was midway through our hectic schedule, ultimately I decided that it would be better fixed in post. Given more time to research the reason, it may have been something simple, or maybe its just something inherent in the build of the adapter.
We did look at the Letus, but there were reports and reports of release dates going back months for the B4 mount. I may be wrong but I think its still not out. So the P+S seemed the right choice of adaptor. But from what I saw, the Letus looks like the solution for the hpx500, if it ever comes out!
Matt