LVM in Alpha caused a nightly email reporting an error about quotas, if I remember correctly. An update stopped the error from occurring, and i ran my Alpha system all this time using LVM with no issues.
I've always preferred a flat file system because some utilities like clonezilla didn't work well with LVM. However, I believe this is no longer true, and although I dont know the benefits of LVM or how to work with it, I suppose I can learn to live with it.
Besides, there was an option in Beta to not use LVM while installing, so I'm thinking this is not a problem and doesn't need the developers to waste time with it.