Surveying eBay, it looks as if a good Orion-15 will run about $215-$250 these days. However another $75 - $100 will also purchase a decent Canon 28/3.5, and a just a bit more money can purchase an Avenon/Kobalux 28/3.5. These are all quite compact 28 LTM's, that are not particularly fast.
The Canon has arguably similar optical quality to the Orion, but the Avenon is undoubtedly a superior lens by any technical metric (based on my direct experience with it and the Canon). Both the Avenon and Canon are also more than a stop faster than the Orion as well.
Therefore it begs the question: Is the Orion-15 worth the current price? I think only marginally so. A few years ago it could easily be purchased for less than $200, but not today. This lens appears to be evolving to more of a collectible lens, albeit one that also has merit as a shooter.
In regards to comparisons of the Orion with the Summaron, some of these comments regarding the optics may be true, but I sincerely doubt the build quality of the Orion comes even close to the Summaron (at least if it is anything like any FSU lens I have seen). On the other hand, the price one must pay for Leica mechanical craftsmanship in this case is quite steep here. The LTM Summaron 28/5.6 seems to sell for at least $2000 these days, almost as much as the new M Summaron models.