Middleton is what most fresher's are afraid they'll get!!
But there are two more blocks (Tees and Tyne) which have just been renovated (Tees, my block, was finished a day before we arrived!) and Weir and Derwent, while not nearly as 'new' as Tees and Tyne, are better than Middleton. So the chances are actually against you getting Middleton (it has about 60 rooms and there are hundreds of freshers)
But to be honest, it really doesn't matter. The only big thing is whether you want a network connection or not (I know Middleton doesn't have them, and possibly not Weir and Derwent either - but they are gradually increasing the number of rooms connected). Other than that, though, you will always make the best of what you get. My block has very small rooms, but they are really really nice; consequently I would hate to have a bigger one. Middleton's are bigger, but there's usually something falling off. But that's just funny! (I know you might not agree now, but its different when you get to uni). There's a really good 'freshers' atmosphere in all the blocks, espeically the older ones. (and the windows of middleton were redone last term, which has made a huge difference)
(And as for the lake - you'll get shot for saying that here!! The lake (and, more specifically, the ducks) are our trademark!! The Mildert Ducks are famous throughout Durham!)
It's a standard answer to everything - but: "whatever you get, you'll love it".