Hypothesis: There is no happier smell than that of bacon frying.
Proof: This morning I tried another recipe out of my most excellent Slow Cooker Cookbook, and it began with the frying of bacon. MAN does that smell good. You can never go wrong when the recipe starts with frying bacon. But it didn't stop there. Add some chicken to the bacon grease, brown on all sides, add some garlic and some fresh rosemary ... and then balsamic vinegar to scrape the bacon bits off the bottom of the pan (I wish you could hear my voice escalating) ... my house smells so good! Everything has been transferred to the slow cooker, but the smells still permeate my being. Yes, bacon is the best.
If you're interested in this slow cooker cookbook (and you are), you should check it out. I bought mine at Costco, but you can find it online if need be: Slow Cooker: The Best Cookbook Ever by Diane Phillips. It really is the best cookbook ever.