I use a Razor Ripsaw with XSplit, and it works like a dream.

If you're suffering bad video sizes, download Handbrake. I did a speedrun of Inside using ultra high quality recording settings and it came out at 4.6gig (versus 600 meg at "good" quality). A quick encode in Handbrake brought it down to 1 gig with zero noticeable quality loss. Handbrake is unrivaled for compressing video size.