Nvidia Shadowplay?

So I just started my Nvidia Geforce Experience thing and there's this Shadowplay feature which seems pretty cool as it records previous gameplay when you weren't recording. But it also manual records, unfortunately it's only for a few games.
Anyone tried it out?

makes the game laggy sometimes (rarely)
however work fine the quality of the record and stuff is awesome

You need a GeForce 6700 or above to use it, so no

i like it a lot, great 1080 footage without impact of fraps

Are the files huge?