I finished earlier today. It looks like there's a lot of extra curricular activity, but I'm not really interested in any of it. Seeing how there's no multiplayer element, I don't see the point of going out to get stronger gear/weapons etc... I'm not going to do that just to fight against the CPU.
One thing I like but also kinda don't, is how you spend most of the main story circling around the same places.
I will say the thing that most impressed me were how well done the interactive fight/cut scenes were. I'm talking particularly about the ones with Bauldur. I could've done those all day.
If you want to take on the Valkyries, you have to upgrade your gear. The queen was the most difficult boss fight in the game without question. Took me over four hours to finally defeat on normal. Just one misstep could cause massive damage, and she moves pretty quick.
I went through the game and collected everything. Had to go online for a few ravens and to find which final artifacts I was missing, but I was so close on my own that I couldn't let the last couple slide. I loved playing this game and the combos get insane after a while. There's so much that I would forget to use them in battles constantly.
Also, the shattered gauntlet of ages fully maxed with certain enchantment stones becomes the infinity gauntlet. It's the best talisman just for the three enchantment sockets, but once you put the stones in it gives you a nice perk that does some pretty nice damage. There's six enchantments where any combination of the three in the gauntlet will give you said perk. The highest I could get Kratos was 9.5.
