Simplescreenrecorder, or shortly SSR, is a quite powerful screen recorder. Especially the possibility capturing games via it's glinject library is, i think, something unique. Even capturing 32bit games on a 64bit system is possible since you can build the glinject libary for 32bit too. On the official homepage there is a good howto capture steam games. 
For those who want to test ssr, there is also a good overlay from Anders Larsson which provides a ebuild for simplesreenrecorder. 
Issues - not really ;)
Unfortunately i also came across two limitations which however isn't ssr's fault but are simply sane restrictions - not everyone has a triple monitor setup. Fortunately the author was really helpful with my "issues" and helped me to get around those restrictions.
Issue 1 - triple monitor:
My first issue  was that i couldn't capture all screens on my triple monitor setup. The reason was because i was hitting the size limit of shared memory segments, as set by:
Simple increasing the size via:
fixed this issue for me. However, MaartenBaert (the author of ssr) said i could hit other limitations as well so this might not work everywhere.
echo 67108864 | sudo tee /proc/sys/kernel/shmmax
Issue 2 - high resolution (2560x1600):
My second issue  was rather a silly one. I simply couldn't capture any game with glinject, which just printed following error:
Fortunately i only had to increase the "Maximum image sice (megapixels):" to 4 (default was 2).
[SSR-GLInject] GLFrameGrabber for [0x13cde30-0x180000f-0x180000f] frame is too large to capture!
Thx again to MaartenBaert for explaining the issue to me!
I also created 3 videos, showing the possibilities of ssr. Even though the quality of the videos are quite bad, it shows three games on my triple-monitor setup. You can find those videos on youtube:
Anomaly warzone earth: https://www.youtube.com/watch?v=vlbMB6n6VSU
Defcon: https://www.youtube.com/watch?v=QSOcXYGL8L0 (i don't know why but on youtube the video had a wrong resolution for me - had to download it to get the correct one)