After playing for a while, I can highly recommend the Skyrim Immersive Creatures mod. The number and variety of critters and enemies it adds to the game is really amazing. Some of them can be really brutal, but I'm looking for a challenge. For example, there are creatures called Draman that look like human/dragon hybrids than can both use magic and breathe fire, and I just started running into mechanical Dwemer dragons that breathe blasts of scalding steam and conjure spider mechs to help them fight. Even the basic animals have lots of new variants. For example, instead of encountering a single bear, you might run across an angry mother defending several cubs, and I've lost track of the number of new types of wolves in the game. Everything looks great and nothing looks out of place in the game world. This mod is a great example of why I firmly believe that Elder Scrolls games are best played on the PC.