To be honest it's a pretty simple design and should work well, providing they're made as well as most Samyang kit. I'd be intrigued to hear how well the metering behaves as IIRC it's a T2 mount. I have an ancient T2 mount Makinon mirror lens which requires a couple of stops of exposure compensation to get usable results, presumably an artifact of the lack of any aperture coupling.

I did look at them briefly, then Dad bought himself a 150-500mm Bigma to go with his K7. For the few times I actually need a lens that long it's easier to just borrow it!

I thought the F series lens bodies were mostly plastic anyway?

From experience it's very close behind the original SMC Pentax 28mm f3.5 - the older lens is sharper at f3.5 but they're even by f8. When I used mine on digital I tended to leave it set to f8 and infinity, then just meter and shoot. Due to the depth of field it was pretty much focus free. I now use it as part of my ultra-compact M series outfit, while the older lens comes out when I know there's no risk of losing or damaging it as it would be a lot harder to replace.

I paid about £50 for mine and consider that to be the usual going rate, at least I would expect to be able to find one for that much with a bit of rummaging.

Both are much, much sharper than the f2.8 versions. I find myself wondering whether this is like the 50mm f1.7 vs f1.4 thing - was the f2.8 intended for reportage work, while the f3.5 was intended for serious landscape shooters who would be quite happy with lower shutter speeds in exchange for ultimate sharpness? It's rather academic anyway as half a stop doesn't tend to make much difference in daylight, even in the depths of a Welsh winter!

Check carefully for fungus inside the lens (usually shows as spidery marks on elements), it seems that lenses kept in the genuine hard cases are more prone to it. It can be cleaned, but you might want to negotiate with the seller if the lens was sold as clean/minty/unmarked/excellent or similar.

Things that make me wish Pentax had kept the full K mount:

My MZ-7 displays the aperture chosen on F/FA lenses when you're using the aperture ring rather than setting it to "A". That said, my KX and MX manage to do the same thing for any suitable lens with a couple of little mirrors...

My LBA became much more controllable when I decided that from now on I was only buying K series lenses (well, aside from an M 100/2.8 and DA 21mm Ltd being on my wish list). Given their rarity and the fact that they tend to go for daft prices now this means that I don't buy many.

Unfortunately in the last week a minty 135/3.5 and 200/4 from said series jumped me. They are very, very sweet to use though...

There's one in Florida, apparently. Pity none of the UK museums seem to want to get theirs flying, but I suppose it'd be prohibitively expensive when you consider the need to maintain it on and operate it from the water (beaching them sounds like a seriously complicated exercise).

The other thing to remember: A series lenses will need you to dial the focal length for shake reduction when you switch the camera on. F series will be picked up automatically like the DA lenses.

I've had similar thoughts of late while looking at my DA* 50-135mm. Obviously with a lens this good you don't want to buy cheap £5 Hong Kong special filters, so I've been thinking about what I really want so I can save for a decent one. So far I've come up with a polarizer, and can't think of anything else. It'll double as a mild ND and lens protector, and by turning the filter you can bring the reflections back should you want them. I don't tend to shoot landscapes with this lens so I don't need heavy duty NDs, and most other effects can be done digitally now.

Providing you stick to public rights of way you've nothing to worry about legally. They might still be stroppy, but you're allowed to be there and can report threatening behaviour or attempts to block the route.

One chap I know had the following technique for chained gates on rights of way: He would cut the chain off (as you're allowed to remove blockages) then hand it over to the local Police station (so that he couldn't be accused of theft - legally they were obliged to take it!)

You don't need the starburst filter now - I think the K-r can do this with the in-camera image editing? I know the K-m can.