This is my first cellular iPad. My previous iPad 2 was wifi only.
I just looked at my first months worth of cellular data usage of the iPad and out of the 3GB plan I have used 527 MB in 22 days (I have AT&T model). That 527 MB was some emails, some web browsing, streaming Netflix, and using the eBay app. I usually turn cellular off and leave it off until I need it. I figure if the companies are going to be a pain with the different data plans then I am going to hoard my MBs and use them when I want/need versus getting all the normal traffic that gets sent to the iPad like notifications, GPS signal, email, etc...
I have an iPhone 4 as well so most of the time I use that if I need to check something. I only switch to the iPad when I am out if I want to use the larger screen to make it easier. I know a lot of people won't like this option but like I said it keeps my data usage down so I pay AT&T less and my data is there if I need it. I have 8 days left in this period so I will probably stream some more Netflix while I am away from home.
. Don't want to just give up those GBs.
IMHO, the companies should just charge $5-10/GB and call it quits at that instead of some of these ridiculous plans. $14 for 250 MB, $30 for 3 GB. I use pretty low data usage each month but never 250 MB. Always over that. Maybe 1-2 GB/month. What if I don't use 3 GB each month but I use over 250MB? There is no middle ground.