The 3G version gives you internet practically anywhere with a monthly allowance of 100MB for free for 2 years via Verizon's network. The WiFi version only allows you to connect to WiFi routers or hotspots which means you can only connect at certain locations while on the go or at your home. If your smartphone supports it, you can turn it into a mobile hotspot which will allow you to be on the internet while on the go, but this might incur additional charges based on who is your carrier.
Verizon by default provides the cellular service, as well as 100mb a month for two years for free. However, the Gobi 3G chip supports GSM networks, and the Chromebook has a SIM card slot, which means that AT&T, T-Mobile, or other SIM carriers can be used on the chromebook as well.
It does require a bit of setup to use a provider other than Verizon. Google has some good information here: http://support.google.com/chromeos/bin/answer.py?hl=en&answer=1059122
Geez, it's not a regular laptop. It runs on an ARM chip, not Intel. If Quicken makes a Chrome browser extension, you are in luck, but you can't just install stuff like on Windows or OSX. It is essentially a browser. I am buying one, so that is not a putdown. I use my Android tablets more than my computers at home, so I can't wait to give it a go. I bought the 3G model when I read about it, cancelling my wi-fi order.