Well I can't answer all your questions but I do have about a nickel's worth to contribute. Back in the day when I was a youngster (Yah the earth was still steaming then) they use to add kidney suet to venison for burger. That was nasty. It's no wonder a lot of people said they didn't like venison! Maybe some members can relate to this. You'd take a bite then chase it with some milk, pretty disgusting. The fat would form a greasy film on the roof of your mouth. Pretty gross. I've done a lot of deer processing in the last 20 years or so and I found that almost all my customers would ask for suet to be added to the trimmings for ground venison but most if not all didn't know there was a difference in the fats. Most just thought that suet was the name for beef fat. I would explain that there is a difference and recommend regular fat from loin, chuck and round. I never had anyone insist on kidney suet. I did however get many many compliments on the quality and taste of the burger that I made for them. I heard countless times from guys that their wives and kids would never eat the ground venison from other processors until they started having me do their processing. I know some of that is due to too much venison tallow in the trim but then add suet to that and yuuuck.

I seem to find much of the same thing in retail. I will always ask what they're using it for and if it comes from a recipe I won't try to talk them into other fats. Usually they don't even know there is a difference.

Some pasty makers use suet in the crust and I've found them to be greasy also. Those recipes are kind of "old school". To each their own but I don't care for that myself.

I've heard that a little brisket fat mixed in burger adds good flavor. I haven't really tried that but I could see where that might be good.

We make "bird balls" using regular fat ground once then mix bird seed and form into a ball the size of a softball and then cover the outside with bird seed. The birds must approve because they sell pretty well.  If the fat isn't ground I can see where suet would work better cause it will crumble and flake off and be easy for the birds to eat.

I don't have any science to add, just personal experience.

Hope this is of some value to somebody

Suet is the fat from around the kidneys and some people would have sold a piece of it when selling kidneys for steak and kidney pies.

Its then coursely grated and used for the pastry much easier to handle than using chilled butter. It makes a more flakey pastry because it melts slower and sort of leaves a bubbley pastry if ive explained it right.

Its also used in dumpling and steamed pudding type recipes.

Its mainly found in the shops here in the chilled section near the butter when you find packets of lard.Atora is the main brand that you see.

http://en.wikipedia.org/wiki/Atora

http://www.atora.co.uk/

Like lard it has gone out of fashion though lard does make the best chips (fries)