Personally, I use the Arlington "Speedlocks" & have never had a problem with them.... I've used the Arlington version of the #2 connector with the set screw & never had a problem with those either... The speedlocks are awesome when you need to fish MC down a wall to an existing J-box.. No locknut to fuss with.. [Linked Image]

-Randy

PS... I get a good reliable ground connection by bonding the ground wire where appropriate, this typically bonds the outer sheath at both ends via the connector & box. [Linked Image]