Hi,
I use istock, and often do get something useable but often I want photos of composers and that is a bit tricky to find.
I also was very particular about my new website wanting just the right subject and colour and bought photos from Getty images and shutterstock too.
Getty were a bit more pricey, but well worth it for what I got.
Shutter stock seemed very good and if you are using a lot it works out very reasonable to buy a subscription.
Site is due out soon. (any day)
It looks great, and most of the functionality is nearly there now.