Wifi plus 4G Hotspot
I'm in a somewhat different situation that may match some others'. So here's my approach. I travel on business fairly frequently and while I almost always have wifi connectivity there are times when I don't. (inadequately wired hotels; client sites without wifi or secured unavailable networks.)
Since I have to have intenet access at all times, I recently upgraded my Verizon data access phone number (linked to a specific netbook I bought from VZW) to a Samsung "hotspot" 4G router. Saves me $10 a month ($50) if I don't use over 5gigs per month via the Verizon network (and I almost never use that much.) and $10 per gig if I go over.
The hotspot router connects up to five devices at one time so I can use it with my iPad, laptop, and phone simultaneously and get 4G speeds. (About 8-10 times faster on the VZW LTE network than 3G speeds.)
It's a perfect solution for me but there are downsides to consider.
() Unlike the month-to-month pricing available for the iPad I have to pay $50 for 5gigs every month whether I use it or not. But since month-to-month pricing isn't available for the hotspot that I can use with other devices, I have to live with it.
() The 4G LTE network is currently limited to about 60 cities (as I recall), but fortunately, my work takes me to cities that are covered (e.g. San Jose, Los Angeles, etc.)
() I could have opted to get the same functionality with a new 4G phone with hotspot functionality and tethering but for a number of reasons I preferred to keep my old phone and not mix my voice functionality with data access. Further, it appears that 4G hotspot speed is significantly faster than 4G service on the tethered HTC Thunderbolt from Verizon. (According to Laptop Magazine, as I recall.) And as I recall, there is a separate "tethering" monthly charge on the phone. (That may be avoidable if you're willing to root your phone and violate your contract. I'm not.)
So, bottom line is that I saved about $130 on the price of iPad and a separate monthly data charge for 3G service when I need it on the iPad. Since I have to have internet access at all times on my laptop, that's a sunk cost of $35-$50 per month (3 gigs is cheaper than 5 gigs.) In return I get 4G internet access on both my laptop and my iPad.