I've found mine to be very comfortable, they haven't really rubbed at all since I've had them and I do a LOT of walking in them. However, as they're flats the sole is very thin, so I have found that adding an insole to give a bit of support to my heel helps. I do walk between 3 - 6 miles most days, though, which is perhaps not advisable in ballerinas
Looks like there are a lot of Repetto fans here. I've worn Repetto flats for years now. Love LOVE LOVE 'em. I've tried Bloch but I've found them to be very uncomfortable. For me anyway. Lanvin didn't work for me either. Whew! Otherwise, I'll be in the poorhouse!
Ferragamo varinas, Miu Miu bow flats, and Cole Haan flats (with Nike Air technology). London Sole ballet flats are also comfy, but they wear out too quickly for me.
Varinas for me were a fail. The leather is so stiff, it wore into my heel and I bleed all inside my $450 flats! They are definitely NOT cheap and not worth it IMO. I really like Tory Burch and am piqued by all the VW Lillian votes. I'll have to try them out