VM needs to offer NON-expiring plans...
It will depend on signal strength but if the signal is good you should get 3 to 4 hours from it during data transfers.
One good thing I would think is that you might be able to put the device somewhere in the room that it gets better access...and it won't have to work so hard to get a signal. With my iPad, on one side of the room, I get a 3g connection...that sometimes drops to Edge. But on he other side of the room, I don't get ANYTHING!
But regarding the notion of the VM WIFI device being something extra to LUG around vs. getting an iPad with 3g, it is not the size of the device that is a turn off...it is that it is yet another device to have to manage. GEE WIZ!!! Life is supposed to be EASIER with the iPad...kind of like...one device to rule them all...not have another device that has to be turned on and off...to worry about running out of juice...or charging up yet another device.
I think it is one thing to tether to a cell phone that you are going to already having to "manage"...but quite another to add ANOTHER device. But, really, the convenience of the built in 3g of the iPad is WORTH putting up with a few limitations. The price is right at least.
Now, when 4g comes to my smaller town (90miles east of Houston), then I may consider tethering to get faster speeds on the iPad...and drop the ipad plan down to $15/mo.
And I think it is a lack of competition that we don't have data plans like long distance calling cards. This business of data expiring at the end of the month needs to change...and it is going to take somebody being competitive and offer a data card that doesn't expire at the end of the month. Personally, I wouldn't support VM for doing it like this.
People should call and say, "Hey, I am interested in your data plan, but not if it is going to expire at the end of the month". Let em know! They will yield if enough people voice their opinion. Unacceptable things continue to happen as long as people remain quiet. So, speak up...they will listen.
I would buy one even though I have ATT unlimited 3g on my iPad, just to have a competing tower to connect to...but no way if the card is going to expire.