6x? hardly. DVD-R tops out at 4x still.
Pioneer's new DVR-106D is a DVD-RW DVD+RW combination drive. It offers a few advantages on the DVR-105, but it is still outclassed by the Sony DRU-500AX and DRU-510A.
The Sonys burn CD-R at 24x, and CD-RW at 12x, and have DVD+RW 4x support (although you'd be hard pressed to find any media).
And once again, Apple doesn't seem like they'll be planning support for DVD+RW any time soon, although if it comes to that, I wouldn't imagine it would be hard to, if they choose to. I recall a few months back the whole thing with the OEM 4x Sony DVD burners that Apple used in the new 17" iMacs were rumoured to have the DVD+RW capability crippled by firmware.