I'm going to buy Skyrim this Monday December 31st when I get paid. I was watching a friend of mine play it for a while, and it looks really good. When you encounter an enemy that you fight in the game, is there any information about the enemy posted in the journal? My friend couldn't find anything listed but doesn't really care all that much. I on the other hand would find that rather interesting.

No...sadly the journal is next to useless thanks to all the quest markers. Anyhow though skyrim itself is badass so enjoy it.

No, there's no way to get any info about the enemies, apart from console commands on the PC. Which makes it pretty strange that many spell's descriptions have the level up to which enemies are affected.

But the rules of thumb are: everything has low armor apart from dragons and chauruses, and everything is resitant to ice damage

the journal is not a journal, is more like a quest Tracking device, Morrowind is the game with a real Journal! wish the next TES as one like that
But interesting? how ? why would your character wright: " i killed a bandit today" (kills other) "i kiled another bandit" i wouldnt do that. but now if it was a bandit that you had a Storie in the past or something like that now that i would wright about when i killed him. although i think there is something in the Pause Menu if you switch "general" to other menu it appears how many people you killed and a few more stuff.

I think he's talking about have information about enemies. For example: Bandit-use a variety of weapons, but have cheap armor.

Falmer: blind, but have poisons and tamed Chaurus.

Things like that perhaps?

A compendium of enemies would be nice, though probably improbable when it came non-monster entities...

Yes, a beastiary that details enemies characteristics and tactics. If it was smartly done it would reveal information about them only after killling certain number of them, or trying different attacks against them.

There are ingame books about ice wraiths and trolls though, so maybe just include those for the more exotic creatures?