The FD-91 does NOT have either a hot shoe, or sync capability built into the camera. Later models aparently do.
This annoys He!! out of me because I have some excellent flash units from my 35mm days. I could really benefit from additional flash from time to time.
I'm also not averse to having the ability to trigger just my gigantic flash to get the croud out of my way. I learned the BIG FLASH pscycology long ago, and it still works. If I'm going to be shooting where I need croud clearing ability, I just attach the big flash, and fire it even though it diesn't really help me take the picture.
The FD-91 is battery only, and it will only use a battery with the "Infolithium" chip. Sony was real cute on that bit of technology. There is an adapter to use the camera with AC power, costing an arm & leg, and only available from Sony.
The battery doesn't charge in the camera on the FD-91.
When I bought the camera, it was state of the art. Naturally, state of the art got better just about the time the camera arrived in my hands.
For the average user, the 14x zoom is probably sufficient, but for me, it was a bit lacking. Then again, I want to fill the frame with a Great Horned Owl sitting in a tree 400 feet away, and do it in lo light to boot. I've gotten lucky a few times. The range doubler and super wide angle adapters are about $40 so it isn't a major investment.
www.pricescan.com has an excellent listing of compeditive vendors on all digital cameras.