Altivec was just fun to work in. Much like writing PPC assembly in general, it felt like a civilized toolbox with a good set of hand tools -- you have your socket wrench of each size (byte, short, int), and you always know what to reach for -- but then it came with just a couple power tools -- vperm and vsel were basically your electric drill and impact wrench, and every once in a while you'd realize that instead of doing a perfectly good job banging out the result with your hand tools you could just finish the damn thing right now with the power tools. And when you could, you ended up code that was shorter, simpler, faster, and easier to write. So rewarding.
The GameCube/Wii vector ISA instruction was not Altivec, and not very similar. It used 64-bit vectors (packed as two 32 bit floats usually), so half the size of Altivec, NEON, and most of its contemporaries. These packed vector instructions shared the register file with the floating point unit (that is, an FP register could contain either a 64-bit float acted on by a normal floating point instruction or two 32-bit floats acted on by a vector instruction), rather than having a dedicated separate register file like Altivec. And most of the fun instructions had no equivalent.
