Everyone says this... but the charts are valuable. I've seen alot of charts and have shot alot of glass. Seeing the charts lets me get an idea of how it will perform. Dustin likes Tamron glass... I personally hate the warm cast it produces vs the Canon. Sure I've learned how to "tweak" the images in post to get it close to the Canon but I'd rather shoot glass that performs like the Canon. Sigma glass does that.
I think if I was to go but any non real world tests, DXO mark lens ratings can be more interesting since they measure lens transmission too. I've also read that every company does MTF charts differently so makes it pretty pointless comparing them if they are from different manufacturers.
I like to just wait and see real world tests and some prefer to see charts, everyone's different.