Understandable sentiments, but hardly something that can be helped. A brand new camera is just as likely to get a fibre/dust or whatever on the sensor as an older one.

To throw my two cents in here though, I agree an Arctic Butterfly is a good investment HOWEVER I would NOT recommend using it to clean the sensor on an brand new K-5 for the first time. Indeed I would STRONGLY ADVISE AGAINST IT! I tried this myself with unfortunate consequenses. The brand new sensor had some kind of residue film on it from manufacturing and the Arctic Butterfly just smeared this around and made a mess, so I ended up having to clean both the Sensor AND the Arctic Butterfly. The first time you clean the sensor, use swabs and solution and give it a thorough going over because this will remove any film which might be present and you'll be able to use the Arctic Butterfly for subsequent cleans without any problems.

Funnily enough I also have the Hoya HMC UV filter though it is the UV(C) version rather than the UV(0).

I use a circular polarizer with my DA 55-300 with no problems. Images are perfectly sharp. The one I use is a Marumi DHG Circular P.L.D.

The 72mm version was highly rated in testing by Lenstip and I've found the results to be good.

Whilst not a 'classic' composition or expected exposure for the subject, I like it a lot. As DrOrloff says the two main elements pull in opposite directions, but for me this adds an interesting tension to the image which underlines the contrast between elements. The rather 'low key' exposure suits the mood of tension too.

It's a really interesting image and sometimes an image which doesn't appeal to everyone can be more interesting (at least to those who like it) than one which does.

Images like this one will never be universally praised because once you move away from the recognised 'rules' of composition and so forth the appeal becomes very subjective. It's just as likely that next time you might do something I won't like but DrOrloff might think it's really good.

I know you're quite new to DSLR photography (as am I compared to most people on these forums) so I hope you don't mind if I offer a word of advice about posting photographs and asking for criticism: Listening to people's comments and taking them on board will help you to take photographs which have a more universal appeal - which is a great skill to have - but don't let it stop you experimenting and breaking the rules too. If YOU like an image you took it's likely somebody else will see the appeal in it too.

When I post images I most often post things I think (and hope) will appeal to a wide audience because the resulting feedback helps me develop my photography skills. However I also sometimes post images I know a lot of people probably won't like - although the resulting feedback is not as useful it's interesting to gauge what reactions different people have.

Perhaps you had a dodgy copy as mine is fine and I've heard (mostly) good things from others too, apart from the known problem with the rear element separation.

Out of interest, do you have any recollection of roughly how much this lens retailed for new?

I have the FA 28-70 F4 and it's a remarkably good lens for its price/weight/size. It's not as sharp as my Tamron 17-50 but stop it down a little and it's really not far off. I'd say it's sharper than the DA 55-300. As an added bonus, my copy focuses noticably faster than either of these other two lenses!

If you want a good looking lens, however, look elsewhere. Its unattractive and cheap-looking grey plastic finish does it no favours.

Any decent 100(ish)mm macro that can focus to infinity (and as far as I'm aware almost all of them - and certainly all current models - can) will make an excellent telephoto prime.

Could do with a 100mm macro.

Personally I wouldn't replace my Tamron 17-50 and DA 55-300 with a Sigma (or any other) 18-250. Useful as it is not to have to change lenses quite so much, I like a lens which is sharp enough that you can still get a decently sharp image after a reasonable (though not extreme) amount of cropping. From what I've seen I don't think any of the 18-250 options qualify on this score. With a lens that goes to 250 rather than 300 if anything more cropping would be needed, and the problem is made greater by the fact that (according to reviews) the Sigma 18-250 performs at it's weakest at the 250 end. It also seems more prone to CAs (again, especially at 250).

To me, these things make a difference in 'real-world' viewing. I'd rather change lenses and 'get it right' than end up with unusable images.

Every Pentax DSLR owner should have a DA 55-300. It is an astoundingly good lens for the price (even the brand new price). It's also incredibly compact for it's reach. I most certainly am NOT selling mine.

To be fair the K-5 is substantially more expensive than the 550D so if I were your colleauge I'd fully expect the K-5 to be the better camera, all othe things being equal.

Having said that I do get the impression with Canon's lower end DSLR models at the moment that they are just churning them out with a focus on features and stats that look good on paper and sound good in sales talk rather than producing models with genuine substance. The K-5, on the other hand, oozes substance (but again, isn't a lower end model).