I'm playing an Xcom files campaign on Veteran, and today I was very busy with the kids so the game was just running with me taking a moment to play every now and then when the situation would let me.
And I noticed that after about 12-14 hours of running (computer was on all day), the game was stuttering and sluggish. Seemed like a memory leak to me, so I restarted the game to see if it was any better, and it was not. I'll try rebooting next, but it seemed report-worthy.
[EDIT] a reboot seems to have fixed the issue. I'd put it down to an OS problem, except that open Xcom was the only thing affected.