Almost everything I have read suggests that the December Verizon support will be a missed target. Mo Versi, HTC VP of Product Management has replied to me stating that they are working heavily with Verizon to try to get the device and network working together, but he did not give me a firm date.
Many sources are suggesting a January or maybe February date for the Verizon support on this device. You would want the Unlocked variant of the phone for this even though there is a Sprint variant. Verizon plans to have this as the first non-CDMA device on their network. I think this means they need to perfect VoLTE or wifi calling to ensure you can get good service on the device without the traditional CDMA for 3g and voice.
My wife didn't want to wait so we switched her to T-mobile and she is very happy so far. If you aren't in love with Verizon, I recommend giving T-mo a shot in your area. For the price, they give you a ton of bang for your buck if you live in a decent enough area.
Best of luck friend!