Look for a Cam (or access module to some) slot in case you find something you want to subscribe to.
A cam will enable decryption along with a subscription card which slides into the cam and then into the slot on the receiver.
I would definately make sure that the receiver has a good range of symbol rates as this can differ greatly among broadcasters. A sky box only has 27500 and22000.
Also DisEqC 1.2 which will enable your receiver to communicate with a motorised dish in case you add this in the future.
Usals is also a good option but not necessary.
Below is some info on Usals from the Satcure website.
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USALS is a calculation system processed by STAB of Italy and given free to all manufacturers of satellite receivers and PC cards. The program enables the receiver to calculate the positions of all satellites in orbit with a precision of better than 0.1 degrees with reference to the installation site. This is achieved automatically without the need for specialised technical knowledge.
Please remember that USALS is a program and not a communication protocol. In collaboration with EUTELSAT, the DisEqC 1.2 protocol string has been defined to drive the motors in "Drive Motor to Angular Position (degree)" mode, which is the only command itilised by the USALS program. The USALS program is, therefore, an advanced option of the DisEqC 1.2 protocol.
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Armed with this information, you should find that this will help in your search for a receiver to suit you.
Enjoy!