I have had this for a few months now. It's fast, easy to use, and saves my thumb. It is one of the best I've used. Do beware that it can potentially leave the cartridges at the wrong angle, leading to mis-feed later. This is not often.
If you're target shooting, no problem. If you're life depends on it, always feed by hand and make sure that the magazine is not rattling and all the cartridges are seated properly...
Pros: No thumb pain, fast
Cons: Beware of mis-feeds
This review was written in the old system and had content requirements that are different than reviews written today.