Originally posted by Winnie I'm not afraid to manual focus, ...but I'm really liking the light meter.
With that in mind I should stick with the F, FA, and A's. Correct? Once we get to M lenses I lose my light meter?
You don't lose it completely with "M" lenses (or "K" lenses, which are functionally identical); you just get somewhat more limited access to it. See the sticky thread at the top of this forum on using manual lenses. Basically, you need to press a button and the camera will momentarily stop down the lens, take a meter reading, and set an appropriate shutter speed for you. So if you're accustomed to using Av mode, this is basically the same thing but you need to hit a button every once in a while (when the light changes).
With all Pentax models *except* the K2000, you can also use DOF preview to get the camera to stop down an M/K lens for as long as you want and show you a "live" meter reading, just as you get in M mode with more modern lenses. But the K2000 lacks that ability, so there is no way to get a "live" meter reading.
So with any model but the K2000, I wouldn't hesitate to get an M or K lens. But with the K2000, while the M/K lenses can be used, I would hold out for the "A".
BTW, regarding MF versus AF - I think it's great you're willing to go with MF. Yes, occasionally a shot might be missed because you couldn't focus in time. On the other hand, shots are missed using AF too, because the camera picked a different focus target than you intended or wouldn't lock in time.
Josh's birthday example is actually a prime example. With MF, you can pre-focus on the cake and be ready to go at the moment of the blowing - and it's "obvious" this is the way to do it. With AF, you can of course use the same technique of pre-focus, but the unfortunate tendency is to simply wait for the moment and then try to shoot, and you may well find AF doesn't lock quickly enough to get a shot off at all - or if it does, it locks on the subject's shoulder or someone standing behind the subject. Having AF available is great, but it doesn't necessarily solve your problems for you. And actually, I find AF without "quick shift" - the ability to instantly switch to manual focus without needing to reach around to the front of the camera to move the lever - to be more trouble than it's worth at times. And unfortunately, the F & FA lenses lack this feature. So the FA50 doesn't strike me personally as being worth 5 times the price of an A50/1.7.
On the other hand, I totally agree with Josh about 50mm being not a great focal length on APS-C. Presumably you became attracted to the idea of a fast 50 because others have written about it, but much of what people have written about fast 50's is in the context of 35mm film, not in the context of APS-C digital. On your K2000, a 50mm would be too long for most of the kind of pictures one might otherwise want a fast lens for. Due to the "crop factor", it's a 33mm lens (or anything "near" that focal length) that provides the field of view for your DSLR that made 50mm the preferred focal length in the "old days".