I always tip housekeepers everywhere but their tip really depends on how good they are. That may sound awful of me, but I figure if you make an extra effort, you get rewarded. I hold the opinion that if you take a job that you know you need to rely on tips, then it's your choice if you get a "normal" tip or a "great" tip or give bad service.....
For example, I had made up envelopes before we went that had $3 a day in them. Now, we are not messy people and just the two of us. I left one the first day, but I also left a note and asked if we could have additional coffee and additional soaps and shampoos. That night when we returned, she had left a ton of coffee and a ton of soaps and shampoo. So I added two more dollars to her envelope the next day and a thank you note. That night, we came in to find my stuffed Mickey and Minnie propped on the bed, with sunglasses on and more shampoo and soap 
So guess who got $3 more dollars added to her envelope the next morning? That night, we came in to find nothing special and the bed half-butt made. (I truly think we had a different person that day), so I left the original $3 envelope. That night, we came in to find our washcloths all cutsie, my Minnie was now wearing my tiara and septor and tons more soap! Ha ha. So we added $5 dollars to that day!
I do this on cruises with non-Disney as well, and at the beach for a week. I'll ask my room steward to make sure we have ice every day. If he does, more money goes in. I've asked for extra toothpaste, because I ran off and left mine, he showed up with 5 on the bed...more money. I've had multiple towel animals before in one day, extra towels, extra chocolate etc. Every time they go an extra step, they get extra money. They seem to catch on quickly and we get exceptional service, so they get extra. Do your standard job, get a standard tip. Our room stewards have figured out if they go above and beyond, they can made $40-$50 dollars off us in a week! It's a win-win. We get incredible service, they get more money.
