1. Wi-fi performance is poor compared to other devices including the older slimdevices kit. 2. Forced firmware updates when connecting to other server - i.e. if you don't keep your slimserver up to date every swap between squeezenetwork and slimserver will automatically run the firmware update procedure.
otherwise worth it for the last.fm and pandora features even if it supported nothing else. (pandora/sirius/rhapsody are US only services at present but with a little tinkering can be made to work via squeezenetwork :))