With one-way satellite systems you can download the data at high speed from a satellite, but in order to upload data (and that includes every time you click on a web site to navigate through it with your mouse), you need either a landline, radio phone, or GPRS connection.
This will cause a problem if you have no landline. Using a radio phone or mobile phone with GPRS will incurr additional costs, which may be prohibitive.
Generally these systems are considerably cheaper to purchase and the monthly subscriptions are less than a two-way system. Such equipment is most suited to situations where a landline exists, but is not broadband enabled.