A few days ago I heard about Truphone (http://www.truphone.com/). They offer mobile VoIP that has been designed for E-series phones. You send an SMS with the word "Tru" to the number given on their web site and receive a test message back with a link to download a settings wizard. Basically this wizard automates the SIP setup on your phone. You run this software and in 2 minutes you're making VoIP phone calls (assuming you're near a WiFi hotspot). I've been using this for three days now and the voice quality is excellent; all this plus free calls to PSTN phones until the end of the year. You can also get phone numbers in the UK or in the US. Given all the effort we spent a couple months ago trying to get these phones working with any VoIP provider all I can say is I wish Truphone had come along sooner.
Mark