We usually tip when we go anywhere. There are just the 2 of us adults and try to keep the room clean as possible. That being said we usually leave $2-$5 a day - normally placing the money on the pillow.
On my birthday trip last year, we were at Coronado Springs - There was a large convention going on at the time, and we were one of a few non-convention guests. Maybe the mousekeeper did not like that we left our rooms later in the morning, rather than at the crack of dawn like many convention guests, but one night we had come home to find the money still on the pillow with the note pad and pen. So the next day, we left it (I think we doubled it), with a note of thanks. Still, it was not picked up. Of the 7 days that we were there, I believe on at least 3 days, the tip was refused!? On our day of check out I think we left $10/$15 - this way it could not be refused.
I don't know if we were under tipping, or why the tip was never received (even with a note), but I kind of felt embarrassed. We did not feel that the rooms were sparkling and never once received a towel character or curtain design (ok fine we are adults) we did not have this issue on our previous visit to this resort!
On second thought, maybe they did not like finding black towels in the tub one morning when I had to clean it! Coronado decided to flush the pipes and not provide notice to the guests (or staff for that matter as anyone we called was oblivious to our calls). As I was preparing to shower, the water pressure dropped off and black sandy water came gushing from the faucet, until finally loosing all water. 15 minutes later the water came back on an all was clear but we were left with a filthy tub!
I think I will try the envelopes for our POP/PO vacation in the fall.
Sorry for the long post !