[mickey]

I've got the 40mm XS and really like it.
Not a huge amount of difference in length between that and the 35, but I noticed the difference when I use my K50.
50mm for me is sometimes too long as an everyday walkaround lens.

It might be necessary to factor in a few other things such as size.
The 40mm makes for a rather unassuming kit, even on a bulky K10; on a K-5 it's very much pocketable.
It was this reason that I chose the 40mm XS for a general walkaround.

[reeftool]

I own the DA40 Ltd. and several 50 and 55's. Of the three choices, I would say a 35 would be a more practical everyday lens (a size I don't currently have) as the 40 and 50's are a little long. My favorite walk around prime a 28/3.5 Takumar.

[monochrome]

I can't say what you should do but I can tell you what I've done

• 1977-1984 my only lens was a K50/1.4. My only camera was a KX. I made that work and I didn't think I missed anything.
• 1984-2001 my second lens was an M50/1.4 that came with an MESuper kit I bought. I made that work and I didn't think I missed anything.
• 2001-present I've bought and sold over 100 lenses on eBay that I always wanted to try and about broke even. Many of them were the various versions of 50mm made by Pentax over the years.
  • 2007-present, beginning with a K10D (crop format) my most frequently used lens is an FA35/2
  • 2012-present, with a K-01 my most frequently used lens on that specific camera is a DA40/2.8 Limited (it just fits).
  • 2013-present with a Q my most frequently used lens has been the 01 Prime - 8.5 mm x 5.5 = about 47mm

For whatever reason I have been quite comfortable around the 50mm equivalent focal length and tend to gravitate there with whatever camera I use but the qualities of the FA35/2 make it my go-to lens. It's the lens, not the FL that makes it my choice.. I've even used it on my film cameras when my K35/3.5 is too slow.

When I didn't have a choice I made what I had work for me. Once I had a choice I chose the lens, not the FL, and made it work for me.

[ChristianRock]

For some reason, I love 28mm Manual focus lenses. They seem perfect for my "Vision".

I also find good old 50mm and 135mm very useful.

This is me as well.

I have 3 28mm lenses since i like them so much, but the Pentax-A 28mm f2.8 is my favorite. It is the perfect walkaround lens. Manual focusing is not an issue, it is very easy to focus. Plus, my copy is very very sharp.

I also like to carry a Pentax-A 135mm f2.8 when walking around. Everything in between the 28mm and the 135mm, I find I can cover using my feet

The 50mm is the perfect portrait lens, so if I know I'm going to take pictures of the family, this is the one that gets put on the camera, and I will take the 28mm along just because I might want to use it.

I don't think swapping lenses is that big of a hassle, so I don't really use the kit lens anymore (18-55). The only reason I'm keeping it is to sell it when I upgrade the camera, as it will probably be easier to sell the kit then to sell just the K20D body... the only zoom I might take along is the Pentax-A 70-210 f4 (in case I want to use the macro, mostly).

[Hattifnatt]

One vote for the plastic wonder, the 35mm f/2.4. Fantastic lens for the price. Tends to stay on my camera most of the time (so far I have the kit 18-55 WR and 50-200 WR, plus the 16-45).

[derelict]

I prefer 28mm as well. I have three different but the manual Auto Chinon 28/ 2.8 gets the nod. I also have a 35mm that never ever gets put on. I usually jump from the 28/ 2.8 to an M42 Auto Chinon 55/1.7 (fantastic lens). I am thinking about starting the search for a wider 28.

[Wingincamera]

Besides the 18-135, I have the DA 35 macro, FA 50 macro, and the DA 70 2.4 Limited. The prime I use the most is the 35, unless macro then I like the 50.