Is it worth it for me to start mining with Deepbit if the best videocard in my studio is an old 9800gt, especially given that I can't run it 24/7 since I use it to test our OpenGL projects? Would I be better off just buying the Bitcoins?
Just friendly advise. Do yourself a favor and give up mining with your current hardware; completely.
The more important advice follows.
Do a LOT of research before you even considering putting one penny into bitcoin. Right now is a rather pivotal time and I would say by far the most dangerous time to considering investing without REALLY UNDERSTANDING WHAT YOU ARE DOING.
I mean this in all kindness, but also I need it to be seen publicly for ALL individuals getting into this market without knowledge.