Here are some feature request I would like to see build in..
- For formats that have high dynamic ranges like HDRI, OpenEXR, floating point TIFF's, It would be nice if the users were able to change the 'Exposure' with shortcuts like [ and ]... i.e. check HDRIShop -- http://www.debevec.org/HDRShop/
- It would be nice if dragging with the right mouse button gives you the ability to drop an image in another application (An ACDSee Classic feature I so much miss).. Of course you can just 'copy' an do 'paste' in the other application.. but.. This draggin and droppin is just something I'm use to.. It doesn't cost you clipboard memory either

- A feature for dual monitor users.. It would be nice if going to 'fullscreen' does NOT center the image. causing one part of the image ends up on one monitor and the other part on the second monitor, which could be very annoying if you're viewing small images and/or if the total border width of your monitors is 10 cm.. It would be better if it just picked one screen (able to set a default) and uses that (and make the other side black or not(toggleable)). This all preferable toggleable cause in cases were images are like 3000x3000 you sort of want to use both screens.
Cheers,
wolv.
http://www.ginodammers.com/