I don't view the R9 style mag catch to be a downside to the firearm. It does a great job for it's intended purpose. I would say it is one of the features that drew me to the gun.
I have carried KELTEC and the LCP and at some point or another I would end up with an unwanted released magazine! This has never happened in my 4 years of daily carrying my R9.
To release the mag, I place the bottom of the gun on a flat surface, push down on the gun, slide the mag release back and the magazine will slide right out.
I also squeeze the gun between the mag and top of the slide, thumb on top and middle and index finger on the magazine. With the other hand release the mag catch.
Once you practice enough with any technique, you will get it down.