Anyone with experience of 15-85 (and ideally 17-55mm, too)?

I just wanted to thank everyone for your incredibly helpful advice – and to apologise for my rudeness in only just now replying.

After reading everyone's replies, I'd thought that I was certain to go for the 15-85mm. But, I hope you won't think I did think something foolish – at the last minute, I decided on the 17-55...

Like dave_bass5, I too live in the UK (and, to make things worse, near ever-overcast Manchester), and I came to realise just how useful being able to use f/2.8 on my 50mm STM has been. (As ddixon mentioned, the 50mm seems quite soft at f/1.8 – I inadvertently came across this chart and was surprised to see how much sharper it becomes at f/2.8: http://www.lenstip.com/444.4-Lens_review-Canon_EF_50_mm_f_1.8_STM_Image_resolution.html)

I think that, knowing I could foreseeably only purchase one of the two lenses, I eventually realised that I would use the 17-55 more frequently, even though the 15-85 would be the best lens for if I were travelling somewhere. I realised that this probably happens much less frequently than I take indoor or low-light shots, though.

I suppose another factor was, with how many times I've read that the 17-55 is perhaps the best EF-S lens, I would have forever wondered if I should have gone with that while I had the chance.

I really am sorry to have gone a different way to what I'd indicated – but I wouldn't want it to seem as though your advice has been wasted. If ever I'm in a position to purchase the 15-85, I feel much more confident in knowing that I'd be buying an excellent lens.

About my 650D's handle squeaking... I think you might well be right. I purchased the 55-250mm not too long after the body and, being my first DSLR, I suspect I made the mistake of walking around holding the 650D by its handle alone, only bearing the weight across both hands when taking a shot. It's something I definitely won't be repeating with my 80D!

I'd been considering the 18-135 for a while (it looks like a fantastic lens) but, when I found out about the 15-85, I realised that I'd perhaps find the extra 3mm at the wide end more useful than 135mm. It's still a lens I'd certainly bear in mind for the future, though.

On a more positive note, I'm utterly amazed by the 17-55. I can't believe how sharp it is – and, against what I'd been expecting, at f/2.8. And I really like its bokeh, too. I had an exam yesterday so, with the build up to that, I haven't managed to use it, or the 80D, as much as I'd like, but I'm looking forward to spending more time with it now.

Thanks to everyone for allaying my fears about lenses of this weight feeling unbalanced, too. The 17-55 feels reassuringly weighty on the 80D and perfectly in balance. I really couldn't be happier with it.

Thanks again to everyone for your help.