My Charter area went all digital about a month ago. Didn't cause any problems at all. (I just had to re-run Guided Setup to select the new channel lineup.)
They also (finally) upgraded our cablecards at the same time so I can use all six tuners.
(Note: many Charter systems are still using old Cisco firmware, so you may be limited to five tuners.)
I'm still not on the latest tuning adapter firmware, which occasionally causes problems. But not very often since TiVo implemented a workaround a few months ago.