Coming from another UW student, it depends.

If you want to go into post graduate studies then yes grades matter. Some companies do look at grades, so it matters to them. But for the most part, especially if you are looking for employment in the software development sector, grades mean nothing. Well...they mean you have good learning skills but that too is subjective from person to person.

I have shitty grades myself, but I do have a kickass portfolio which is what lands me jobs. Simply put, if you have nothing to show for your skills, then people will look at your grades. Hence if you have an awesome portfolio, dont really worry too much about your grades, but do ensure you pass and clear your semesters :)