I've got an MSAR E4. I've been surprised by it...I didn't think I'd like bullpups but wanted to try one out. It is incredibly handy, I love that the compactness of it. Muzzle rise is less than an AR due to the geometry. The trigger has surprised me...much better than I thought.
Mine had a few minor troubles in the first few 100 rounds but MSAR customer service is impecable. They bend over backwards for you. All troubles are gone. Bullpups won't replace traditional rifles in my safe but I appreciate them when pure compactness is required.
As for Steyr vs MSAR, MSAR has continually product improved the rifle and are being very innovative and responsive to customer requests. The company is reputable (Microtech knives are their background). If you absolutely must have a Steyr, buy it. But I wouldn't hesitate geting the MSAR.
Also, I made a podcast review of the rifle. Take a listen, let me know what you think
http://gunreviewpodcast.com/msar-stge4-kris-from-southwest-michigan/http://gunrightsradio.com/forums2/index.php?topic=2767.msg19985;boardseen#newMSAR StGE4

Me shooting my E4

Size comparison to other 16†barreled rifles

MSAR 30 round mag, USGI 30 round mag, CMMG 42 round mag
