To say that as long as you can see the satellite you will be able to get it is not entirely true. The lesser the angle for reception of a satellite signal the greater the need for a larger dish. Small dishes simply will not receive sufficient signal under those conditions.
The other factor is the LNB, you will receive the satellites that were available when the LNB was built, however if it was not designed for a new one coming on line, then you again will not get the signal even if you are right under the satellite.
One of our satellite providers recently put a new HD satellite in service, thousands of LNB's are having to be replaced to receive that new satellite. It's footprint has been greatly reduced for coverage in the US compared to the other two owned by Shaw and will not be available to Canadian subscribers very far south of the 49th.
There is much more to receiving a satellite than simply seeing it, as mentioned there are websites that provide considerable information on the subject.