We just revamped our MP-1 at the beginning of the year and we do think its the best thing out there. FWIW its turned into our best seller- outselling our cheaper preamp 10:1 and outselling the amps too.
I think its better than anything I've heard, including fm acoustics :), *but-* I found that some people want something darker, especially if they are running bad digital, or they want something simpler (our stuff is fully differential and balanced and although works quite well with single-ended amps, its an uphill battle...), and we don't have any transformers in the circuit and there are actually those who will not accept an audio piece if it has no transformers (which I regard as a filter). Then there are those that want remote control, and are willing to sacrifice sound quality to get it.
And finally- I've not heard everything out there. There would then be the question: would I allow that something else is better, given my predisposed position as a designer and manufacturer? I'm not sure I can answer that, and the fact that I've not heard any better over the years can't be evidenciary, as I could be biased or our gear really could be that much better.
So the bottom line seems to be that even if you *know* in your heart of hearts that you have the best, that the reality of the culture is in fact that the best cannot exist! God could have made the preamp, and there would be those to accuse it of being too dark, too bright, too boomy, too bass shy, etc. The "best" does not exist in that world, it only exists by individual declaration.
It would seem to be a hopeless case, as there is therefore no meaning in making improvements, but I have found that when situations arise that seem to have no meaning, you have to play the game all out so as to be a player rather than a mere occurrence, IOW even if the best does not and cannot exist that I choose to try to make the best and do that best I can anyway. Sort of like Sisyphus...