This has nothing to do with 3G. It just flat out disables your APN meaning no data access. Sorry, I guess there's a little confusion on my part too because I'm a Milestone and not Droid user. It's a pretty clear cut difference for us EDGE vs 3G UMTS/HSDPA. The software doesn't disable your 3G APN only, it's disabling your APN entirely. You're not getting data whether its EDGE or UMTS/HSDPA at least on my Milestone.
And it should work the same way on Verizon. It's not disabling your EVDO-A (3G) data, it's disabling your data entirely.
So I suppose you can receive calls still if its just disabling your APN, but I would recommend changing the OP and not mentioning "3G". I know the graphic it self says 3G with an X on it, but it's not killing your 3G in any way to my knowledge. Otherwise you would still be getting data via 2G/1x. So in that sense yes I was confused based on reading the OP because it is somewhat incorrect. The developer's site mentions only disabling the APN btw, perhaps their icon is too confusing, and most people correlate 3G to data when in fact it's just a different communications protocol.
I'm just a little bummed because here on ATT we always talk about 2G vs 3G and iPhone users talk about turning off their 3G to save power. I just thought that this would be the app to turn off my 3G when I'm not actively needing it. But this is a little different.... I guess completely shutting off data.
In some way I find this pointless as you could just disable push and change all your apps to use data polling. You would essentially be doing the same thing. If you pulled all your email and facebook updates you would be doing what Juicedefender is doing... at least the free version. I can't imagine why your phone would be accessing data otherwise when your screen is off.