I've never experienced New Years Eve in Cumberland Valley, but from what I hear there is a lot going on!  It sounds like First Night Carlisle should be a lot fun, and there is still plenty of time to get an admission button. There is also a dinner at the Holly Inn, which is now under new management, that should be fantastic.
I haven't gotten a chance to sample the new cuisine at the Holly Inn, but I have glanced at the menu and everything sounds excellent. They have also booked Mileunder to play classic rock throughout the evening.  Roundtop Resort is also having a New Years Celebration with lots of family activities and events for people 21 and over. At the Midway Skating Center in Carlisle, they are offering 5hrs of skating, from 10pm-1am, for 5$ which is a really special way to spend New Years Eve (and the first part of 2012)! And, of course, you can always attend the Anchor Drop in Shippensburg or the Wrench Drop in Mechanicsburg!

Whatever your plans, and I hope you make it a plan to attend AT LEAST one of these events, have a wonderful New Years Eve and a fantastic beginning to 2012!