Thought I might report my experiences now that I've tried a few times.

I've been meditating for 20-30 minutes each session, and so far haven't gotten much out of it. I've found that when I'm depressed it's much easier to meditate, presumably because my mind is already somewhat slow and blank. When I'm not depressed I usually find myself getting impatient around the 15-20 minute mark. I've found it somewhat instructive to observe how allowing certain negative thoughts to rise causes an affective response in me, which I can then completely halt by returning attention to my breath. Other than that, no jhanas, no sense of disassociation, nothing except the awareness of sitting around concentrating on my breath. Since I have quite a lot of free time at the moment I'll be continuing the experiment anyway.