Almost perfect
Simplenote has avoided the temptation of feature-creep and stayed, well, simple. It synchronizes, it shares, it keeps notes. It does one thing, and does it very well. If you want to keep notes across Mac, iPad, iPhone and web, I dont know of a better option. I use it daily, and share notes with my housemates so we have common shopping list, to-do list, and so on.
I say "almost perfect" because Id really like markdown support, but thats a minor point.
b_e_n about
Simplenote, v4.4.1