We did it in August and really enjoyed it. I have done both Wishes and Illuminations.
We'll never do Wishes again.
We will do Illuminations again. Doing it again this month for that matter, though this time it was part of our Package at Epcot for F&W. We'd still have paid to do it again too.
No you don't sit, though we did sit on the rail behind our table. And unlike Wishes, you don't have to leave where your table is to watch Illuminations. So if you have a spot to lean or sit you can stay there.
The desserts at Epcot blew everything at WDW out of the water.
The one at Epcot has adult beverages. Not great ones but it has them.
The view of Illuminations is much better than the view of Wishes at WDW. Never will understand why they put you off to the side. You pay and you get a bad view? Crazy.