I used the one that came with my SR45 when it was new and the mags were really stiff and it worked fine, but now i just load them the old fashion way before i go to the range.
I've never used those silly things...what I have done is taught myself to not only rack the slides one-handed but also load the mags one-handed with either hand.
I tried it out just to see if it was worth keeping in my range bag. It will work in a pinch so I keep it on hand just in case my Uplula gets left behind.