I’ve used them many, many times. In fact, just got my tickets in the mail last week from them. If you sign up for Mousesaver’s monthly newsletter, there is always a link in there with an extra discounted price, specific to Mousesaver patrons. So, you get a discount and pay no tax. For a 6 day parkhopper that I just purchased from UT, I saved $35.00 per ticket compared to Disneys new prices plus tax. Also, you can add the ticket to your room key if you are staying on site. After checking in, go to guest services and they will add it on.