Don't worry — the design is essentially the same as the Calendar you've seen for the last few years.
Most everyone will be auto-updated on either Jan. 8 (for those that have the Rapid Release update option) or Jan. 15 (for those on the default rollout update option). Some folks may wish to opt-out until Feb. 28 — but after that, Google will auto-update those holdouts that are afraid of change hesitant to part with the older Calendar (Google's upgrading options can be found here)* Read more...