We did a Wishes cruise last fall and it was amazing. We had heard mixed reports about Illuminations cruises (they seem to be real hit and miss) but the Wishes cruise was beyond our expectations.
I believe the smaller boats are $225+tax, and although we only had 4 people we opted for the larger boat with audio which cost $275+tax. We figured heck, for the extra fifty bucks we might as well go all out.
You meet your driver at one of the Marina's (we picked the Contemporary, but you can chose any of the three MK resorts), where he whisks away your credit card and returns with your reciept, and you head to the boat. They ask you to be there about an hour before the fireworks, and your scheduled departure is usually 30 minutes before.
On the boat are drinks and snacks provided as part of the package (canned Coke products and small bagged snacks like chips, etc.), but you can also have the meal catered with dinner or dessert, etc. at an additional cost.
The driver takes out for aproximately a half hour around the lagoon, telling you all about the different areas, Disney history, etc. (this depends on the driver and your wishes, if you want to just sit back and relax without the spiel you can get that too). During this time you make your way to the MK area in time to view the fireworks. Post-fireworks, you get another little tour on your way back to your original starting point. Takes about 60-70 minutes for the full ride.
Check out AllEarsnet for more info, that's the site I used when planning it and they had some great information. For a more reliable experience, I highly recommend the Wishes version - I can't imagine anything more magical.
AEfx