There are a few places where you can find images by lens:

Here you can select by lens. Some images here though suffer enormously from the site being redesigned and images rescaled from smaller, original submissions. So I would concentrate just on what you think are the better images.

Select from the list of tags.

How Pentax users rate their lenses. There are example images provided too.

Personally the appeal of Pentax for me is largely for the prime lenses. From the zoom lenses I do rate the DA12-24, which I own. However, it is not weather sealed and I believe the current price, which was hiked last year, is too much. The DA*50-135, which I also own, has superb image quality, the downside of the lens is the AF, which is very disappointing for tracking moving subjects. If AF is not important and you rarely use long zooms then the 50-135 with the superb DA*300 combination is worth considering. From images I have seen the DA*60-250 looks pretty impressive, it is bulky though. The DA*16-50 also looks very good but beware SDM failures on earlier examples (ditto 50-135). I've never used one but personally I don't much like the results I've seen from the DA18-135, but it is undeniably a very convenient range. As IQ is paramount to you then it would definitely be a try before you buy.

There are some interesting new zoom lenses on the horizon, for 2013 or thereafter, including a wide zoom (10-25 ish. You can download the lens roadmap from here. I would expect weather sealing.

I've looked at the Oly12-60 flickr group. I wouldn't say it beats Pentax zooms hands down.

They don't look identical to me.

However, in the real world I reckon that there are many things to be done to improve an image. Upgrading to a K5IIs is one of them but it would come way below things like getting up early.

I need to have a much more productive year next year, I only took a handful of good shots this year so I need to get my finger out.

That's not level. It's difficult to judge horizontal without a horizon but there are plenty of reference points on the buildings to set a true vertical.

It's not just professionalism and money. Sites such as 1x and 500pix are by their nature competitive. To get an image accepted into 1x is a competitive process. A picture on 500pix is rated and ranked on various galleries. There is a competitive element here, obviously with the competition, but even with the regular gallery. Simply having a viewcount and comments function adds some element of competitiveness. How that is interpreted is highly individual and variable, but it is there. Sometimes I care about how my images are regarded, rated, whatever. Sometimes I am simply curious, sometimes I really don't care and sometimes I'm just plain messing around. So the competitive element varies for me. But it's there.

Well Bill asked a long, detailed question and I gave a full answer. I thought it was good question worthy of consideration/debate.

But I really don't mind if anyone wants to ignore long replies

I dust spot and get rid of the odd small little edge of frame annoyance, twig, leaf, etc, or the odd bit of litter or something that might have esacaped my attention at the time.

I have tried cloning larger things, just to try but I am completely rubbish at it and the results look awful.

Personally I wouldn't want to remove anything from a landscape. If there are pylons or anything else there than I will either make them an integral part of the composition or I will try to find an angle where they are out of frame.

I don't have any moral objections to removing anything from a scene, but I just don't see the point in doing it.

I have only ever cloned out one larger object from a photo and that was a little bit of a campervan that foiled my attempts to obscure it behind the bridge that was the main subject.

I do tend to spend a long time considering scenes and I try to get the composition right in the first place and the same goes for cropping too, neyond minor crops for levelling and peripheral intrusions or to end up with a pre-envisages format (square, panoramic). I am moving to prime lenses more and more so I tend to reserve heavier cropping for instances where physical movement and choice of lens is restricted. My main 'philosophy' is to end up with as many pixels as I can. I would rather chuck a shot away then heavily crop.

I think over reliance on cloning or cropping or both will just make you a lazier photographer, much less inclined to get the right shot from the outset and will blunt compositional skills.

I don't have any moral objection to adding things to a picture or compositing, there is a huge skill in doing it seamlessly. I don't see the point in changing skies, I think it is far better to get the best results out of the conditions that you are presented with.

I hadn't heard about that controversy of the LPOTY. Looking at that link my immediate reaction with that shot was that the shadows look very wrong, they just don't match the rest of the light. I'm amazed that the panel of judges missed it, it just seems obvious to me that something looks fundamentally wrong. I've heard good things about Charlie Waite, surely he should have spotted it.

I've added the odd Moon to a shot, although the Moon shots are mine too. Done well they can really enhance a scene. It's something I'll probably do more of and I have a number of 'fake' scenes in mind. To be honest sometimes it's the only way to 'compete' with a lot of the shots on the likes of 1x and 500pix, not that that really bothers me. Ods it cheating? yes, do I care, no.

Good question. Sod all the pretty butterflies and sunsets. Just the snaps of the kids, the albums of testaments to the past and the drawer full of old, torn, creased and faded assorted ancestors are by far the most meaningful.

Back in May I took these two photos of my nephew and sister in law just a few minutes apart:

First one is the standout for me and two is good.