I do use FIMO for some stuff, sure. It works, but its different from Green Stuff on how you should treat it. Theres pros and cons.
It says it evey package. I believe its 130ºC for 20 minutes, but I can be mistakes. Just check the package, it says in the wrapping plastic.
You can use FIMO to sculpt large figures or even smaller ones. I've seen great stuff done using it. You can't use it, however, to fill gaps on miniatures and that sort of thing, as you will have to cook it to cure.
Fingerprints wont disappear only by cooking it. If they are there, the will remain there. You can avoid them, though, or correct them.
1) Dont touch the mini while its fresh: make a good armature with a nice base;
2) When the sculpture is done, use a soft brush and give it a light coat of baby oil or White Spirit. It will remove them if its well done... I you over do it, though, it will 'melt' the details too, so be carefull;
3) After cooked and cold, you can easilly sand it to remove the fingerprints.
4) It is cheaper. A pack of Fimo Soft costs 1,60 euros and I'd say the ammounts are not that different. You can choose from loads of colours, including some with glitter and glow effects.
I can't recommend any online store for this. Around here is available in most art/craft/office/school material shops. I can link you to the official site though, and you can see for yourself the main characteristics of the product.
http://fimo.com
Please note that FIMO, even after cooked, chips a lot easier than GS, specially for the smaller details. It also gets all gooey when its cooking and after that, while its still hot. Don't touch it until its fully cold or you will ruin the details and/or cracks will start to appear.