One important distintion between Verizon and AT&T or  T-Moble is that concurrent voice and data work on GSM/UMTS platforms (AT&T and T-mobile) unlike CDMA providers like Verizon and Sprint.
For the lowest prices you may want to look at some of the prepaid  and tier three providers like Metro PCS, TracFone, etc. Prices tend to be lower. another alternative is using a data only SIM in a smart phone

I also use the Mifi but purchased mine at Radio Shack for about $149 in September and activated it in the store through Virgin Mobile for unlimited internet access ($40/month)...and I can turn it off if I don't need it and then back on when I do.  Virgin uses the Sprint network to access the internet and if Sprint isn't in the area it then uses Verizon. I have had 2 other campers use mine at the same time without a noticeable drop in speed, and I now use it in my stick house too. My landline service through Verizon used to cost more per month and have slower service!  

This is actually a pretty good deal. The current advertised rate on the Virgin Mobile Web site is $50 per month. However, if you purchase the top up thru Walmart.com the charge is $39.98. With this service there are some things you should be aware of:
Virgin Mobile US was acquired by Sprint in 2009, and is one way for Sprint to be a major player in the prepaid service segment without cannibalizing their own more profitable post-paid lines of business. The way Broadband2Go data service works is that data sessions are metered, and once you reach 2.5 GB of usage during a 30 day period your service will be throttled back from typical down-link speeds of between 600 kbps and 1,400 kbps, to 256 kbps or less until either the end of the 30 day period or you top up your account (pay for a new 30 day period). To put this in perspective, at an optimal thru put rate of 1,400 kbps, you can download HD movies for about 4 hours, before the service will be throttled for the remainder of the month. The average movie (90 minutes) file size is about 700 MB for standard definition,  1.5 GB - 2.25 GB for HD or 13 GB - 40 GB for BluRay .  Our coach has two TV's and two BluRay players that are wifi compatible for downloading movies. Not to make too much of this, it is worth noting that most of us are not the type of users where this will normally be a problem, as long as we are not downloading movies. When in a park or campground with wifi service it may be best to turn off the mifi device.
The other problem which exists for most RVers with most of the wireless carriers data plans, is how or even whether  data roaming is handled. Virgin Mobile is no exception, in fact, they have ignored all questions on the subject for the last 18 months. So if you head out east on I-90, you may lose data coverage when you leave Spokane until you reach Eastern South Dakota where coverage resumes.

For any "hackers" that don't mind playing around with the technology, here is what I've found to work for me.

I have a AT&T unlimited data plan on my iphone 3Gs.  I "unlocked" and "jailbroke" the phone so I could add non-apple applications.  Cydia, is a source for these non-apple approved applications and they have an app called MyWi, which works great to allow PC's and other IP devices to connect to the internet through the AT&T data network.

I turn off wireless on my notebooks and use bluetooth to connect to the MyWi iphone.  Anywhere I have AT&T service, I have internet at no additional fee.  I think the MyWi app was $39.00 one time fee.  You can also use wireless or USB to connect to the iphone for higher speeds than BT, and I do that when I'm downloading large video, etc.

Check with Verizon for more info but I dropped my MIFI 5G plan to their 3G plan last fall and it goes for around $35. Veterans, ask for your discount.

We just got an I-pad 3G so far so good. You can get data plans starting at $15 per month from ATT or a Verison plan neither plan has a commitment so you can start and stop it. It also uses WiFi if available. Pad was under $700 for a 16 gig. Just wish Apple and Adobe Flash would get along.

Richard/Babs...

Another reason I decided to Jailbreak my iPhone: You can run FRASH, the non-apple approved FLASH support.  Apple and Adobe need to get over it and learn to play together.

Quoted from Jim Casazza

Richard/Babs...

Another reason I decided to Jailbreak my iPhone: You can run FRASH, the non-apple approved FLASH support.  Apple and Adobe need to get over it and learn to play together.

Does anyone know if you can run FRASH on the I Pad and how to jailbreak it?

Note: Jailbreaking an Apple Product can void any warranty.