Sets of 10 reps result in a good mix of myofibrillar and sarcoplasmic hypertrophy.  This makes 10 rep sets an excellent muscle building protocol, but only moderately useful as a strength builder.  Like any parameter, if you use 3x10 for too long it will become ineffective.  But if your primary goal is to gain muscle then 10 rep sets can be an excellent addition to your weight training program.

3 sets may or may not be enough volume to cause significant hypertrophy.  It depends largely on how the sets are performed.  For example, if all the sets are performed to failure then 3 sets will probably be enough for most people to gain muscle.  However, if the first two sets are treated as an extended warm-up, and are therefore not performed anywhere close to failure, then it is likely that 3 sets will not be a sufficient stimulus to gain muscle.

Other factors to consider when choosing the number of sets for an exercise are the volume of the rest of the workout, the overall volume of the training program, and your individual recovery capacity. 

We cant generalize too much if we want to be accurate, but for most people in most situations 3x10 performed with a 10-15RM (the most weight you could lift for 10-15 reps for one set) will yield significant results until your body has adapted to this program.

Always remember that anything can work for a short period of time.  Designing weight training programs that provide long-term consistent results is the trick.  The 3x10 protocol is no exception.

So if you are looking for a good protocol to gain muscle then 3x10 may be the answer.  But if youve already been using it for a month or more then it may be time for a change.