A few thoughts:

- A real letter will probably get more attention (and better results) than an e-mail.

- I question why you continue giving business to a property that has consistently made mistakes with simple things like the proper crediting of points for your stays. I understand that you were happy with the little "bonus" for their screw-ups, but you shouldn't be too surprised that if they can't get THAT right that other things are handled in a loosy-goosy manner as well.

- I don't think that going to the front desk "furious" on the day of check-out was either smart or warranted. "Annoyed," yes at having to correct an issue you thought you had already addressed, but "furious" is a bit over the top (and may have led to the hotel staff concluding you were a fruitcake, making them less likely to want to help you).

- Compensation? Hah! Personally, I think it's always best to write a letter detailing the situation without asking for anything in return. Otherwise you just come across greedy. Be objective in your letter, keep emotions out of it, and see how the GM handles the situation. If he doesn't offer, WITHOUT PROMPTING FROM YOU, to make you happy, then it's probably time to find a new hotel in the area to give your business to.