I have been a Vonage user since August 2003. I am always in the $24.99/month unlimited local/regional plan which also includes 500 long-distance minutes. The monthly usage since I started to try out Vonage are (from most recent month): 386, 383, 341, 1098, 681 and 1025. Because most of the minutes are local/regional minutes, I never exceed my monthly quota. (I did pay some international long distance fee but Vonage IDD rate is very reasonable.)
I just became aware of a new Vonage $14.99 plan that offers 500 minutes anywhere in North America and after that, 3.9 cents/min. By simple calcuation, it seems that if one can keep monthly usage under 756 minutes (500 + $10.00/$0.039), switching to the new plan certainly makes sense. Therefore, I can keep the recent usage pattern, I can profit from moving to the new plan (there is no switching fee or whatsoever). 756 minutes is a pretty high bar for me (it is like 25 minutes talk time every day) so I will probably move soon to the new plan. I hope to shave at least $5 if not $10 per month from my monthly bill and the savings will certainly go to my CFI scorecard.
(BTW, if you want to try out Vonage, give me an email and I can sign you up thru the Vonage referral program: both you and I will get one month's of free service. I promise to respond within 1 business day.)