First, the list of good things, condensed from Shenannigans' excellent comment:

1. No more cost for time and passage via the ferry.
2. Easier access to stores (including grocery stores and the Mac store).
3. Closer to mainland friends and family.
4. More roads to travail with your bike!
5. Nearness to your parentals, who need you.

And some I will add:

6. Cheaper commute by half.
7. I can transfer my cable without penalty, and keep my current services.
8. A trip to IKEA!
9. A park, City Hall, my bank, a stellar bistro, three diners, True Value and the movie theater all within two blocks of me.
10. Close to my favorite hiking areas.
11. The Stillaguamish River, with three or four great swimming holes
12. Proximity to at least 6 school districts should I need to look for teaching work

Any others?