I have one of the early ones, with the M4 style stock and fishgill handguards.
The only problem I've had with it is a small tear in the rubber dust lips (through which the charging handle cycles). Sig replaced it and included a straight charging handle in the process.
Otherwise, it has been accurate and 100% reliable.
It's a little more front-heavy than most ARs, but not unmanageable.
Since new, I've changed out the buttstock for a VLTOR and replaced the fishgills for "Swiss style" 550 handguards, and installed several sight setups. I also installed a Magpul MOE trigger guard, which required enlarging the front hole (no turning back now).
Overall, it's been a pleasure to own and use.
God gave you a soul.
Your parents, a body.
Your country, a rifle.
Keep all of them clean.