What Do I Need from Picture Browser?

The basic functions like thumbnail view, copy, move, full screen view, slideshow, 90 degrees rotate, crop, and others are obvious.
And what I need additionally?
Histogram (all three channels) - it's very useful and powerful tool to study and evaluate a picture. I often use the logarithmic histogram instead of linear histogram in GIMP. Unfortunately I haven't find this option in any picture viewer. I appreciate highlights/shadows clipping.
I also need to be able to grade pictures (five star system) and assign metadata like keywords, etc. (see Which MetaData Fields I Fill Out to Describe My Photos? and Compatibility of Star Rating).