Depends what you want out of the Isles... some quiet sight seeing, mad partying, beach lounging or all of the above?
This site is central for anything Isles...http://www.visitgreece.gr/pages.php?langID=2&pageID=254
I am told Santorini is beautiful, as is mykonos. I went to Ios. You should only go to Ios if you are down with debauchery.
My one advice is to take the slow overnight boat from Athens. It's cheaper, you get to sleep under the stars (if you want) and you get to visit every island (they stop off).
Additionally if you are inclined to scam the system (which I should have done), simply buy the ticket to the first island, and avoid the ticket guys, and you can travel anywhere the boat goes.
Vincent: "So what you gonna do?"
Jules: "Well, basically, I'm just gonna walk the earth."
Vincent: "What you mean 'walk the earth'?"
Jules: "You know, like Kane in 'Kung Fu'...go places...meet people...get in adventures."
Trips (only counting recreational travel):
FIRST TRIP (2005): FIRST EUROTRIP EVER! UK, France, Spain, Italy, Germany, Holland
SECOND TRIP (2007): First Solo Trip! Greece, Turkey, Syria, Spain
2008: China (Beijing, Shanghai, Yangshuo) ...right before the Olympics!
2009: Japan & HK, Southern Spain
[size=1]2010: All over Lebanon, Ibiza (Spain), Oktoberfest (Germany), Thailand.
2011: India (Goa), Jordan, Jerusalem, San Sebastian (Spain), Amsterdam (again), London, Driving from Vancouver to L.A. (stopping in Portland, Seattle, San Fran and all the little stops), Montpellier (France), Geneva and Lausanne (Switzerland)
"Bite off more than you can chew, then chew it."