Like everything else in the “tactical” world, tape switches on handguns bring their own unique challenges and issues to the table. The biggest is accidental light discharges.
As I stated earlier, light is a target indicator. You want to use a minimum amount of light when you are searching a structure or doing something similar because you don't want the bad guy to know where you are. Tape switches are easier to use on purpose than rocker switches, but the downside to them is that they are also easier to use by accident than rocker switches, which can lead to lighting yourself or your teammates (if you do the CQB thing for a living) by accident.
The consequences of this can range from being a minor inconvenience to alerting the enemy to your presence and getting yourself and/or team members killed. The consequences for the average citizen or law enforcement officer are typically going to be on the very low end of that spectrum, thus I would say that the higher risk of light AD's with tape switches is a good trade-off for those individuals (like myself) who find that rocker switches don't work well for them.
I stated earlier that I prefer the tape switches used by the Surefire X series lights and now I'll explain why: Many tape switches out there are held on to the grip of a handgun via an adhesive, or Velcro that is glued to the grip and the tape switch with an adhesive. These do not tend to be good long term mounting solutions, and they don't offer the freedom to take the light on and off of the weapon at will.
The Surefire X series lights, however, have the “DG” switch which is molded around a stiff metal insert that is specifically designed for mounting on a particular type of weapon. This means you can take the X series light (an X200B in the pictures) on and off of the weapon at will without worry. You also don't have to find ranger bands or similar tricks to hold the switch on the grip of the weapon for hard use.
Now all of that is great for those who have a weapon with an integrated accessory rail, but what if your weapon doesn't have one? Thankfully the various light companies have realized that there are lots of people out there who don't have rails on their handguns and have figured out various aftermarket solutions for this problem.