What's been your average data usage the last 3 months (you can get this number from your Verizon account online).
I was using about 2 gigs consistently but since Singplayer came to Android I've been pushing closer to 4. I just rooted last week so I'm sure Flash content will push me closer to 5.
I do use it quite a bit at work. I try to stay on Wifi at home to offload the data the widgets use but I'm not sure how much of a dent that makes.