@Ryan: that seems like a valid solution, thanks! I'll be implementing it in most of our projects from now on
.. and for the record, I really hate inconsistency too. It's just that quite often inconsistent image sizes are something we have no control over; this happens when content is either fetched from a third party with varying level of consistency or added by not-exactly-web-savvy content authors..
Like I said, generally I prefer to control these situations with styling rather than scaling, so whenever an image really needs to be of proper size I place it inside a container -- horizontally and/or vertically centered, depending on situation. This has worked for most situations so far.