My specific application: I often travel overseas for months at a time. While there, I typically pick up a local pre-paid cell phone for day-to-day use and leave my Telus phone off to avoid roaming. To keep in touch with Canada, right now I use Skype or Google Voice to periodically call into my Telus voicemail for messages, and to return calls.
Rogers One Number would let me do this without incurring long-distance Google Voice charges, with the added advantages of outgoing calls having my correct caller ID, and being able to send/receive text messages. If Telus doesn't have an equivalent feature in the works, I will very likely consider switching to Rogers before my next trip.