There used to be a diet on T-Nation (might still be around) called the "MRP Diet". The pros? It was a simple diet - little planning and preparation. The cons - it was expensive and you had to stomach shakes all day long.
My advice is to do whatever it takes to meet your goals (in this case, dietary goals). If shakes are the answer, go for it.
However, in my opinion, and all-shake diet falls into the "extreme" category which, for me, do not fit into long-term health and fitness goals.