Yes, though I haven't scanned everything in Hunters due to all the variants and it's hard to keep track of them all. I do enjoy it though, moreso in the GCN Prime games. I call people like myself "Scanaholics".
Yes, it's interesting to what actually happened to the planet you are on and why it's like that. If you didn't scan anything in MP, you would be VERY confused on everything and MP2s scan logs tell about how the GF fell on Aether, The pirates failed attempt at getting Phazon on aether and their encounters with Dark Samus. Finally they tell everything about the Luminoth and how they fell because of the Ing.