My wife attended DAK with me and had a great time. She met a lot of other people whose significant others are going to be there in the fall, so it was a good way for her to meet others going through the same thing as she will. Of course she also met the future students and current students and SOs. There is one great advantage of bringing someone along, they JV group did a long housing tour on Friday. They went to far more places than you could see on Sunday, so your BF could really narrow your search down for you. My wife really had narrowed down our housing options so Sunday I only really needed to look at one place (we have a dog so our options were rather limited).
They dont have to go to everything, there are lots of social activities to keep them busy and will give them a feel of what the school and people are like. Even if you are living apart chances are he will be visiting you more than you will be visiting him, thats at least what I gathered from couples living apart. Its a lot harder to go away from the school area for a weekend than to take a weekend away from the office. I met MBA2010's bf and its nice to meet people like that even if they wont be around. Now when he comes to visit I will already know him and it wont be as much introductions and he can just slide right into a group of students and other significant others without much effort or feeling like an outsider.
There is also a mens subgroup from what I heard, no where near as many men as women are involved but they do "guy" things together. They werent really represented during DAK but they are active in a lot of things. SO's can join all clubs and take part in all activities and trips (Ski and GIM) and many go on KWEST (where you cant say who is the student and who is the SO, what you do for a living, basically anything about your background).