I haven't stayed there since it became the Regal Sun Resort, but I stayed at its two previous incarnations, The Dutch Inn and The Grosvenor. I only ever had a problem once in about 15 stays there and it had more to do with my flight being delayed 5 hours than anything the hotel did wrong. Transportation to the hotel from the airport is your choice of rental car, cab, limo or Mears shuttle. Once you're there, you'll have use of the normal WDW Buses, just be aware that your bus will have stopped at the other DTD hotels first before getting to yours. Make sure that in the morning you leave relatively early so that the bus won't be as crowded, otherwise you may be standing on the ride to the parks. Regal Sun is the last or second to last stop for the DTD buses. This also means when you leave the parks, it will be you getting off of the bus last. The rooms, if they haven't changed much, are your standard hotel room. Nothing really special about them, but if you don't mind heights, I recommend springing for a tower room with a view of DTD. Makes it so you can see the fireworks at Epcot from your room in case you don't feel like fighting crowds that night. The breakfast is a buffet with your typical selections along with one or two special items that they'll switch around each morning. A couple of mornings each week, they have Pluto and Goofy come around to the tables at breakfast as well, which is a slightly cheaper alternative to a full on character breakfast at the Parks. And it's nice to be able to walk to DTD in the evenings if you feel like taking a break from the Parks at night. Overall, I've liked staying there, but again, haven't stayed there since it became Regal Sun, so your experience may vary on the service at the hotel, but everything else should still be the same.
As for the buses, I seem to recall them being every 30 minutes throughout the day.