Three: No limit. No cap but poor coverage Beware that O2 expressly forbid video and audio streaming on their 3G network. so that means no skype calls or youtube on the go. Also note that iPlayer only works with the 3G networks of Vodafone and Three at the moment. But since the N900 is crap at iPlayer, thats negligable. and when they do release flash for the N900, you can always use wifi regardless of network. Three allow audio streaming including Skype but you have to pay extra for that service on top of mobile internet service .