Except for tomkeet being in prison of course, given that photographing banknotes is illegal

As far as test charts go, the only one I bother with is testing for front/back-focusing, from focustestchart.com

I own the 10-20 f4-5.6, and when I bought it a few months ago I had the same dilemma so I'll give the advantages of each as I saw them then:

10-20 f4-5.6 (old one):
*Sharper
*Better distortion (old one has 'weird' distortion at 10mm and then is fine for the rest of the range, while the new one has barrel distortion for more of the range)
*Lens is cheaper (by about £50)
*Cheaper and easier to obtain filters (77mm on this vs 82mm on the new one)

10-20 f3.5 (new one):
*Faster (one-and-a-third stops at the long end), which could be important for interiors or lowish light (though remember you can go down to 1/15 shutter speed at the wide end!)
*Silent HSM focusing
*I think, though I'm not certain, that it has quick shift (ie the ability to use the manual focus ring while in AF mode)

I was originally looking at the DA12-24 but gave up when Walters (the last store to have them at what I considered an acceptable price) sold out. It really is stupidly expensive now, but is faster than the old version of the Sigma 10-20 and sharper than both versions.

However, having gotten used to my 10-20 I am glad that I didn't get a DA12-24, because I find myself using the Sigma at 10mm the majority of the time: the Sigma 10-20 takes much better photos at 10mm than the DA12-24 does

Are you using a specific focus point or Auto (or 'Whole Scene', or whatever on earth the one that isn't a specific focus point is called )? This is one explanation (other than "it's the lens") for only your DA 12-24 having problems: with it being much wider than your other lenses, perhaps the AF system is struggling to determine what should be in focus?

Or from an online retailer which pays for return postage on faulty items.

What on earth did you buy a weather sealed lens for man?

This was primarily on Canon mount, because apparently Canon's AF routines are more difficult to reverse engineer or something along those lines. In fact Sigma lenses which are fine on other mounts* still occasionally have FF problems on Canon.

*i.e. it isn't a fault with the line like with the 50 f1.4

Just ordered one - spoke to SRS on the phone and they were quite happy to delay sending it until Thursday (though they can only do this for Mainland UK). I'll of course let everyone know how the Sigma turns out!

See, HDR isn't just for cityscapes with weird cartoon colours

Decided to get one - tipping point was that I checked the photos I thought had been at 200mm, and they were actually 105mm (whoops!) so right within this lens's good performance range. The fact that it's on a good offer (hey, I am a Scotsman!), weighs half as much as the Tamron 70-200 and goes as wide as 50mm (which I really like as a portrait FL) didn't hurt either. Cheers folks - now just have to bite fingernails until tomorrow morning to see if they've still got any!

Certainly looks the part, more so than 'white lenses' IMHO.