said by Mashiki:The hardware itself in the 6121 is more stable and they're better at dealing with upstream channel bonding than the 6120's. But there won't be any updates until there's a need for an update to be pushed. If the 6121's are stable, and there's no need then they won't push anything out the door.
Besides there's a good reason why you can't grab updates and randomly apply them. You can cause network issues.
Wait so the SB6120 aren't good with upstream channel bonding? I'm going to get a SB6120 for $90 this weekend, but if it's not good, then I'll consider spending a bit more and get the SB6121 or the DCM 475.