i have one in my 62, sound quality is MUCH MUCH better for AM. For FM it's a little better, but maybe thats b/c i have crappy ancient paper speakers. With new speakers the difference might be greater. The fact that there are subchannels per station like MTV and MTV2 is quite nice. I think its a worthwhile investment, if it doesnt cost too much more..
I have the JVC KD-HDR1, really like the interface, plays MP3s as well and has an iPod interface. I don't know if the HD sound is that much better than straight FM, sorta depends on how many HD stations you have and whether or not they carry the programming you want. Regardless, it has really good sound.