Yeah, the 'C02 is a *very* worthwhile upgrade!
The extra instructions and new address modes make a real difference! And the pinout changes (compared to NMOS '02) are easily manageable.
As an aside, it's worth noting that the modern C02's made by WDC, though an excellent choice for many applications, are IMO not the best choice for dropping into an existing NMOS project (especially a home-built). You'd be better off with an older 'C02 if you can find one, such as those made in days of yore by Rockwell, CMD and others.
To be clear, many hobbyists have used the WDC chip and had no trouble. But the older devices have much gentler rise and fall times on the outputs, and thus are less prone to noise problems and flaky operation that can result from construction and design shortcomings. Another benefit that helps avoid noise and flakiness issues is the TTL compatibility featured by the inputs on older C02's but not on WDC -- more on that
here.
-- Jeff
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In 1988 my 65C02 got six new registers and 44 new full-speed instructions!
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