At Orange Bus we're strict about following best practices, and in my day to day workload that pretty much means perfect mark-up and optimised graphics.

I've covered the importance of using sprites rather than separate files for web graphics before, and we follow this practice on all the sites we build. For me it's not all about making the download-time faster for the user (although that's a must!) but also a unique timesaver - it makes the maintenance of the site, and the build of the site (not to mention browser compatibility) much much faster. It never fails, a client will ask for minor tweaks when you think you're ready to launch a site, and for me to be able to open one file to alter all the graphics is much quicker than going through an endless long folder of small 1px files is vital.