It depends how you use the opportunities on the scheme. When I did it, there were some useful topical discussions/panel sessions and also the opportunity to network with firms. Some of the tasks were useful to help understand the kind of work a commercial law firm does. So it's very much a case of it being as good as you make it - it's not something to attend just to put on your CV as I don't think it adds much aside from showing your commitment to learn.