Thanks for the report, but this is not a bug, the feature is working as designed.
From its inception, the zoom feature within browserlab was intended as a way for users to look at sections of the screenshots more closely, it was not intended to match zoom behaviors within the various browsers. What we do is simply scale up the image on the client. I don't think we've ever had a request to allow testing of the browser zoom functionality through BrowserLab. Is this something you actually need?
Thanks Mark...I very much appreciate your response.
The short answer is YES!
I walked into a clients store the other day and I was showing off my latest beta website and immediately it struck me that it looked crappy. He was using an HP widescreen and computer that came preinstalled with fonts set at 125% of normal and using IE9. Several of the png's were not scaling very well and had unwanted shadows at the edges. At normal resolution it looked perfect, but if the user chooses to run with large fonts (or if the OS comes preinstalled that way) then things do look so great. This is when I started looking for software to test my websites in different browsers and at different zoom factors.
It seems odd that people could get their knickers in a twist over pixel-wide differences in different browsers (I'm assuming the rationale for the current design), but wouldn't be concerned about how things look when the defaults have been changed to automatically zoom to a "non-normal" size. With the introduction of wide-screen monitors and Windows now coming pre-installed with larger fonts, I think the ability to test in larger sizes is critical, especially for the "perfectionists" out there. I don't often find people who say "I usually browse with Chrome, but when I open I open your website with Safari, the body is shifted one pixel to the left." I'm more likely to hear, "did you know that on your website some of the text is clear, and some of the text is smudged," and then I'm left sitting there going, what is he talking about?