I've been taking practice tests for 3 months now, I haven't done a writing section. I plan on reading up on what constitutes a good essay a day or two b-4 the test. If I don't do well on the essay, it'll go along well with my 2.75 english/literature GPA.
I have done writting samples for only one of the three self administered practices i've done. I have done the writting samples in all of my kaplan practice MCATs however, I have only one of them graded.
I think its a good idea to do at least one practice writting for two reasons.
1) gives you a good idea of exactly how the timing works in the afternoon and how you feel for the upcoming bio section.
2) helps you figure out a strategy for doing all three things required.
Yikes! I took 5 full length practice tests (under timed conditions) before I took the MCAT last year. I always did the writing sample! I think you should NOT skip this section for 3 reasons:
1. You'd be shocked how easy it is to run out of time. True the WS is not weighted that heavily, but you don't want to end up with a K or anything!
2. To simulate the test, you should take the whole test. Writing those lame essays back-to-back is kind of draining. If you habitually skip the WS you may be amazed by how tired you are by the BS on the REAL test day.
3. It's one thing to read what "they" look for in a good essay, but it's another thing to do it--practice makes perfect.
I know preparing for the MCAT is a slog and the temptation to cut some corners is strong. But sheesh, you don't want to have to take the bugger AGAIN do you?? Give yourself every chance to do well--practice the WS.