Personally I like keyboards that do this because you can tell which midis are professional or not. Kar files are usually pretty poor unless they used to be professional midi files without lyrics which were later added to them (sometimes incorrectly as well)... but still worth having...

The thing is, with the newer keyboards such as the PA80, they recogise KAR files automatically and will display lyrics however you have to trust to your ears to tell if its done well or not...