I went on the RS 13 days tour of Turkey in May. Loved it. The tour starts in Istanbul, which is easy, and ends in Izmir, which can create questions. The RS information about returning to Istanbul and/or Istanbul Airport (IST) is a bit sparse and could use some beefing up. The morning the tour officially ends, the shuttle bus goes to Izmir first thing in the morning, i.e., 8:00 a.m. and the bus ride takes approximately one hour. (RS info doesn't tell you this). It's important to know this for booking return flights. We were able to get on the 10:00 a.m Turkish Airline flight back to Istanbul, with no muss or fuss, even thought we had booked on a later flight. They were not squeamish about the amount of baggage either. They checked both my bags with no extra fee. Love Turkish Airlines. (They also give you a decent snack!)
If you have an international flight, please do not make the mistake of booking from Izmir to the Sabiha Gokcen Airport (like I did). the Sabiha Gokcen is located on the hectic Asian side of Istanbul and does not have easy ground transportation. To get to the IST from Gokcen I was told you had to get a bus that took you to Taksim Square and then another bus to IST (this would have been with luggage, etc.) I had bought a ticket to Sabiha Gokcen because 2 months beforehand it was cheaper. When I switched gears and bought another ticket a week before the flight, I purchased it for half the first tickets price. Much easier. I also went directly through the airline and not Expedia, et al.