ive only been to Istanbul and Pamukkale, but it was well worth the trip.
Turkey is much bigger than people think it is, and if you really wanted to see all of it you'll need to give yourself a few months. heck, if you just wanted to see everything in istanbul you'll need 2 weeks if you wanted to cram everything in - but probably close to a month is best!
summer is quite hot in turkey (well maybe not hot for me, but probably hot for you), and probably humid along the coasts, but check out the temps and weather to make sure.
Istanbul is a lovely city. Its clean, modern and very european, with a mix of middle eastern/islamic influence, as well as plenty of history. There wont be a day where you would sit down to do nothing. Of course the biggest atractions are the Aya (Haga) Sophia and the Blue mosque which are quite literally acoss the road from each other and the Basilica Cistern which runs underneath the city streets. Then you have the Grand Bazaar and the many different stores that sell everything from turkish lights, to leather to carpet. Dont forget the delicacies, the kebabs and the turkish sweets, and turkish coffee.
I didnt go to ankara, but i caught an overnight coach to Pamukkale, The coaches are quite modern and clean, and used a lot by many tourists and locals alike. There's a central bus station in istanbul where all bus trips start from called Autogar. That's where you buy all your bus tickets, instead of pre-booking them from the states and getting overcharged. There's plenty of different tour operators, and numerous bus companys to choose from.
as far as renting a car is concerned, if you are pressed for time, catch overnight buses because you can sleep on the bus overnight, and you'll also save money on a hotel for the night which probably would be cheaper than hiring a car, paying for petrol and paying for a hotel room. of course you dont get the flexibility of seeing the country as much, so it really depends on how muchtime and money you have to spend.
i have friends who have travelled to turkey plenty of times, i can always ask them for any specific info or questions you have.
is theres places you must see, its Istanbul and Pamukalle are highly recommended and ive been told that Copadocia is fantastic.
heres a link to my trip to Istanbul and Pamukkale
http://www.tfproject.org/tfp/members...-istanbul.html. if you have any questions, please let me know and ill be happy to help out.