This is almost entirely a frivolous feature request, and probably isn't worth that much effort. However, I thought it might be useful, so I thought I'd mention it.
I was scanning through diffs and blame files, trying to find a particular bit of code. The file in question, unfortunately, is sort of long.
So I was thinking: wouldn't it be nice if you could view the source, and if you held down the Ctrl key and moved the mouse zoom wheel, you went to earlier or later versions? (Presumably without the Ctrl key down should just scroll through the code as usual).
I'm sure this is harder than it seems, as you'd have to somehow keep aligned where you are in the code. Still, I can imagine situations in which it, or something like it, might be useful.
In general, I'm pretty happy with the product. At the moment, I'm mostly using the CLI tools, but may end up using the website more.