There are many pros and cons associated with buying a cell phone, whether it is Contract or Pay as You Go. In UK, Pay as You Go has been very popular now that the mobile operators have realized that it is a realistic solution to draw in a younger market. Most of the Pay as You Go options that I am aware of in the US are quite frankly ludicrous due to the fact that the operator who supply them are still trying to take too much of a cut. Take for example this section from Verizon Wireless' Pay as You Go small print:

Ninety-nine cents daily access will be charged and deducted from your account even on days you do not make or receive calls. Verizon Wireless will suspend service if you do not have the ninety-nine cents required for your daily access, when your account balance reaches zero dollars or your account balance reaches the expiration date. Unlimited IN and Night minutes not available when your account balance has been suspended and subject to termination, at which time Verizon Wireless may charge up to thirty-five dollars activation fee to re-establish service. Any balance remaining at expiration will be removed from the account. The INpulse card is not valid unless initialized by the date on the back of the setup card. Service availability depends on the phone model.

Unfortunately, INpulse pricing is not available with analog-only phones. Voice mail setup and retrievals are billed at regular INpulse rates and will deplete minute allowance when calling from your wireless phone. Charge per call for 411 Connect may vary when not on the Verizon Wireless INpulse Coverage Area. Restrictions and limitations may apply. Automatic connection and enhanced services are not guaranteed at all times or in all areas and rates may vary when roaming on another carrier. For connected calls, the part of the call that occurs prior to connection may have different rates from the part of the call that occurs after connection. Additional toll/long distance charges may apply. You can make three requests per call and get automatic call completion for one requested telephone number at no extra charge.

Using Get It Now, download charges may apply to application download. Airtime charges apply to application downloads and use of some applications. Use of Get It Now is subject to the Get It Now License and User Agreements. See Verizon's website for more information on Get It Now. You may be charged for downloading Get It Now applications. Charges vary by application and applications vary by phone. Get It Now-enabled phone is required and may require a connection in the INpulse All-Digital Rate and Coverage Area. Coverage limitations in maps at Verizon's website. Where applicable, airtime, roaming and other charges may apply when browsing, downloading, using and removing certain applications. Subject to Get It Now Agreements. Existing Verizon Wireless prepay customers will forfeit any unused bonus minutes in their account when changing to the INpulse Calling Plan.

There are far to many extra cost associated with this, that in the end you would probably end up paying out more than you would on a low monthly contract. I would sugest that you take a look at the contract phones available to you from different operators, I know that Verizon has very good coverage right accros the US, there are some very resonably priced deals available that would be a lot less hassle and, in the long run cheaper than the Pay as You Go option.