Never really got into mewithoutYou but I do have to say the song (at least the way that KevDev did it) was pretty good.
It's actually not terribly different than the original. The song relies a lot on the vocal melody, so I'd definitely encourage you to check out the mwY version.
I agree with you. However don't forget he did cover Nirvana's Nevermind. But I do want to reiterate that he should cover other songs and make an album of that.