C++ FAQ Celebrating Twenty-One Years of the C++ FAQ!!!
(Click here for a personal note from Marshall Cline.)
Section 13:
13.1 What's the deal with operator overloading?
13.2 What are the benefits of operator overloading?
13.3 What are some examples of operator overloading?
13.4 Is operator overloading supposed to make the class' code clearer?
13.5 What operators can/cannot be overloaded?
13.6 Overloading operator== to use string comparison?
13.7 Can I create operator** for to-the-power-of?
13.8 But which operators should I override?
13.9 Guidelines / "rules of thumb" for overloading operators?
13.10 Creating a subscript operator for a Matrix class?
13.11 Should my Matrix interface look like an array-of-array?
13.12 Part two of making my Matrix interface look like an array-of-array?
13.13 Designing classes from the outside-in vs. inside-out?
13.14 Overloading prefix/postfix forms of operators ++ and --?
13.15 Which is more efficient: i++ or ++i?
[13.8] Okay, that tells me the operators I can override; which operators should I override?

Bottom line: don't confuse your users.

Remember the purpose of operator overloading: to reduce the cost and defect rate in code that uses your class. If you create operators that confuse your users (because they're cool, because they make the code faster, because you need to prove to yourself that you can do it; doesn't really matter why), you've violated the whole reason for using operator overloading in the first place.