What is your evaluation of the design? For a first iteration it's good. There is room for improvement but I think use needs to guide that. However, I feel that the library should use MPL standard operators instead of creating new ones. This has been discussed and deemed impossible but it is not. What is your evaluation of the implementation? It seems to be slower to compile than competitors by quite a margin. On the other hand, this library is more generic and can handle arbitrary dimensions. What is your evaluation of the documentation? More instruction on what constitutes a unit and quantity so that a developer may override these concepts and use them with the library. What is your evaluation of the potential usefulness of the library? It would be more useful with runtime conversions. I don't believe static conversions will be that useful. Did you try to use the library? I played with it, I did not use it in any real project. With what compiler? MSVC 8 and g++ Did you have any problems? With optimizations on full the library performed almost as well as a double. Next to 0 overhead but not quite. Without these optimizations it performed quite poorly, which could make debugging difficult. I could not find enough optimizations with the Microsoft compiler to make this library usable; 0 overhead was definitely not 0 overhead. Compilation overhead could be a bear for large projects. How much effort did you put into your evaluation? About 10 hours in which I tested various performance issues and tried to use it in various ways I need it to work. It performs moderately well but unless I can find the correct switches for the MS compiler it won't be useful to me. It also doesn't do everything I need and even after digging through the implementation I am not sure it will be useful or easy to even extend it. Are you knowledgeable about the problem domain? I do not work in a real time project where precision is of utmost importance; in fact we often round values. I work in fluid flow analysis, which is true scientific computing in the sense that it is a set of "close enough" guesses to predict the real world with a fairly high degree of certainty. This needs to be fast, so can't pay the expense of constant conversions, but doesn't have the same needs as some of the issues that have come up in discussion. Do you think the library should be accepted as a Boost library? I do not believe it meets the need of a wide enough audience, no.