I guess it was just hearsay then. I'm not much of a gamer but my friends never seemed to have any complaints and I do recall mixing and matching now and again (though on what systems I'm going to be second guessing from now on). Apparently the Gamecube had region protection as well.
Nintendo's home consoles have always been region-locked, via intentional hardware differences on the NES/Famicom, SNES, and n64, and via software means on everything newer. The Game Boy line and original DS (including DS Lite) are not region-locked at all. The DSi is regioned for DSi-enabled software, including DS/DSi hybrid software like Pokémon Black and White. The 3DS is region-locked in software.
Up to the 3DS, I could play games from anywhere (I like Japanese games a lot). I have happily purchased three different generations of Nintendo portable machines and the software to go with them.
