Ah, but it really is nothing but trouble.
When GBASP switched to rechargables, did you see anybody saying "Wow, I wish this could use normal batteries?"* The only time anybody would even think of such a thought would be when they were on an airplane or something and the ride was longer than GBASP's battery life. But with a console, you're always next to a place where you can recharge. I see normal batteries as a major step backwards. Wavebird is a great controller, but a rechargable one would be even better.
*Believe it or not, that grammar is correct...