It's definitely the best 77mm lens ever!
And perhaps it's the best lens for it's size to performance/FL too. But I also agree that, if nothing else, some Leicas outdo it.
Originally posted by Urkeldaedalus I think part of being a prime shooter is appreciating the personality that every lens has, not necessarily its numerical test chart performance, but the actual images that it is able to create.
Yes - I don't choose a lens from my kit just for its FL, but also for the characteristics of the images it creates. If I have to adjust the FL I will. As a simple example, when snappy color is my top priority, I'll try to use the FA43 (or maybe DA15). OTOH, when shooting a Civil War cannon, I'd lean toward the K200/2.5 or K50/1.2.
But to the OP, to address your real question - yes, it might indeed collect dust in your bag, unless you're willing to change your approach to shooting a little. Two things it might have going for it, however:
1) It's smaller than any quality zoom you could have, so you can carry other primes along with it and swap them (e.g. DA15 and FA43 are small too).
2) It's faster than any zoom you have, and is one of the few Pentax lenses that performs so well wide open. It actually could be the best choice for some situations, even sometimes for sports (here's an example where almost all of my photos were from the FA135 or FA*85, showing that a 77 would work well too. A few of my top 85mm shots were when I opened it up to f/2.2, which you can't do with your zooms. See the 'Highlights' gallery and click on the information icon hovering over the upper right of the photo to see the FL used:
http://www.racetimephotos.com/XC/DanaHillsInvite2012 ). Sometimes two cameras, each with a different prime, is your best bet. Even a used Pentax 2nd body for $200-300 can do the trick.
Here's my best guess at a short list of Pentax-branded lenses that might win you over. The ones you've tried aren't going to do it for you. While I've not tried the mitakon, the Tamron is too big (plus it's no faster than a * zoom) and the FA50/1.4 has the worst sharpness I've ever seen in a prime for its first ~1 1/3 stops. Just start with one of these:
Any *300
Any fast 200
F or FA135
(Maybe) DFA 100 WR
FA*85 or FA77
DA*55 (so much sharper than FA50/1.4 for the first two stops)
FA43
DA15
But after all this, I have an even better tip for you: Try an A100/2.8 (or M100/2.8) first - especially the A, since you appear to like some automation. The A100/2.8 is similar to the FA77 in many ways - a small, light, unobtrusive lens with a retractable hood yielding great IQ and backgrounds. If you don't fall for it, you won't appreciate the FA77 either.