I don't know that GSW need to make this trade. I remember first seeing the trade and thinking that GSW would trade Russell as soon as they could or when Thompson came back, but the more I thought about it, the more I questioned this initial reaction.
Part of the value of Russell is the long term contract (4 seasons). Unless you think Russell is going to end up being a bad contract (does not perform up to the contract), I don't think Beal is enough of a short term upgrade to warrant the trade. Now if you are not that sold on Russell, then sure, flipping him for 2 years of Beal is a good deal.
I have come around to believing that Curry, Russell, and Thompson are going to be a formidable trio. Ideally, Russell understands and adjusts to more of a distributor role but in any case, he will be more of a facilitator than Beal even will. Russell will probably become the primary ball handler/initiator, if for nothing else, to take some load off Curry. That doesn't mean that he turns into Rondo, pounding the ball and looking for assists, just take the load of getting the ball up and the offense started. Then the ball should just move.