What does each cellular connectivity indicator mean?
The "o" means that you're on a 2G network. In Verizon's case, that would be 1xRTT. If you see it on an AT&amp;T device, that means you're on GPRS.

Here's a screenshot from the iPad User Guide detailing what the various signal indicators mean:



"3G" means exactly the same thing on the 1st generation iPad as it does on the 3rd generation iPad. However, if you have AT&amp;T, the 3rd generation iPad reports HSDPA+ as "4G". Since the 1st generation iPad is incapable of using HSDPA+, you will only ever see 3G or below on that device.