Notes is one of several possibilities (Notes, TextEdit, and Stickies). You'll probably find TextEdit is closer to the Notepad equivalent, but Notes and Stickies each have their own, unique charms.
How do I access TextEdit? I click the TextEdit icon I added to the Dock. TextEdit is set to Open on Login, and I leave a document open at all times - one click on the Dock icon, there's a note ready and waiting.
All these programs are very low maintenance. They all auto-save, and as with most apps, if you leave documents open when you close the app, they'll re-open when you open the app.
Leaving either TextEdit or Stickies open at all times will cost you about 17mb of active memory, Notes uses closer to 30mb, but in any case, I don't think it's a bad price to pay for the convenience.