Personally, I found it to be a worthless experience. I am a bit biased as that was my lowest grade, to be sure, but I finished in the top 10%. So take from that what you will.
As far as my experience goes, I found that format was key to success, substance of your arguments be damned. I think this varies considerably between schools, but probably not too much. Ultimately, it was a pain in the ass. At my school, appellate writing is addressed in a 2D class (which is optional if you solicit), so we ended with a trial brief. My lowest grades were on the memos and my highest grade was on the trial brief. The best part about the program was the research component, which I found to be practical and enlightening. Apart from that, eh.
As an aside, it is far less intellectually demanding than any of the substantive courses (including lightweights, such as Torts and Criminal Law). I was not very impressed by the legal writing program here, obviously, but success in legal writing will not save you from a shortcoming in, say, Contracts or Civil Procedure. Assuming that the credit distribution reflects this (i.e., 3 credits for writing, 6 for Torts or other substantive courses) focus your energies on the substantive courses. I spent way too much time on LRW, and not enough on other courses, in my first semester.
And, finally, even though the LRW readings are a bore and , well, worthless, read them at least a week before you start writing your assignments. Format is key, and following the format of the examples usually leads to success.