First, to address spork's request for additional info on broken slide catches, I will say that I have personally seen several slide catch / releases break...two Glocks and several 1911's...the Glocks broke springs and the 1911's all had the little extension that goes inside the mag well break off. (Colt had a bad run of these during the early 1980's, but I have seen other brands do it as well). In addition, there are any number of reasons why an otherwise properly working slide catch / release may fail to lock the slide to the rear at some time or other...while not "common" with well maintained guns fed good ammo, it is not something you can stop to analyze in a fight. I happen to think that with the proliferation of Glock pistols...no flame there since I own six at this moment...the technique described by NickDrak is probably a good habit to cultivate if one shoots several different makes / models of handguns. I will admit, however, that I usually use the lever myself...habit.
Extended magazine releases also have their problems, as do weak mag release springs such as those used for several years by Sig and the even weaker ones used in the early runs of M39/59s by S&W. Extended buttons may be easier to reach, but that also makes them easier to unintentionally engage with ones grip, or by getting bumped hard on a car door, or maybe during a physical struggle preceeding use of a firearm. They can also create issues if the longer button causes the other side of the catch to run out farther from the frame when used. I have seen officers have problems with this using the extended Glock release buttons...the gun hand grip actually prevented the catch from releasing the mag with a couple whose hands were large enough that they could hit the button without shifting their grip on the gun. Like extended slide catches they can also snag on things if used on a CCW gun. Early M39 and 59's would sometimes allegedly release the mag from pressure from a seatbelt being tightened...most definitely NOT good with a gun using a magazine safety!
There is sometimes a tendency for all of us to think that because WE have used a particular modification, piece of gear, ammo, or whatever with no problems...usually only on the range and often then only for a few hundred or couple thousand rounds...it must be trouble free. It may, indeed cause no problems in that specific environment, yet be a major problem in other uses or situations. Guys like Lumpy, SGB and many others here know this. Like Will Rogers once said..."Everyone's ignorant... just on different subjects". The great thing about this board is that we can learn from one another...Helluva lot cheaper, too, I might add!