I think it has potential, but it's still not enticing enough for me to get it yet. Maybe when the summer game drought is over and more games come out in the fall and the DLC starts rolling out more people will get on it. I my opinion they should give every PSN member a free trial period like XBL does to see if people what it.
The Pile Bunker looks like a VS size needle or drill, It should be located of the little ditch that runs along the middle of the stage and/or on the left side of the side where the Cat X first appears by the VS suits. But you don't need it to beat the Cat X only to get the "Good Job" for that stage.
I personally would like to see a night stage and have the Night Vision Googles brought back.
They should have mode similar to capture the flag, where it's free for all and any person has to hold the flag as long as they can.