i'm a fan of eggshell, b/c it has enough sheen to be washable w/o much issue and also not terribly shiny so as to show every single flaw in the wall.
i like the paint/primer paint of behr or valspar, personally. i have had great luck color matching SW & BM paint colors with these (even painted our basement mostly w/behr but ran out and DH bought valspar and it matched no problem).
i don't really keep up with the SW paint sales due the above, but wouldn't be surprised if one is coming up, since updating spaces is popular in the boredom of winter.
I prefer Satin paint. It's not that much different than eggshell in all reality though. I need the washability and I like a bit more sheen than the avg. person I think.
My favorite paint is Ace Hardware. Basically because it's the closest to me, easily accessible and affordable. Paint is really personal and subjective though. Everyone has their love and hates. I don't mind Behr for example it's just not anywhere near me. I hate Valspar becuase of the smell and the watery-ness of it but other people swear by it.
Usually I like flat finish, but my go to paint is Sherwin Williams Emerald and that doesn't come in flat. I use the matte finish for everything except for trim. The coverage is amazing and it's very durable.
Not sure when the next sale is, but I'd guess MLK day as well. You can also call the store and ask them.
I like flat paint in areas where I don't have to wash the walls (LR, halls, bedrooms). It hides flaws beautifully, and it allows for touchups without showing any streaks/marks. I like eggshell for the areas I need to clean more like the kitchen/bath. I like regular Behr. I've never used SW. I used some BM from the previous owners and really couldn't tell that it's any better than Behr. However, I went back to BM to buy some matching paint for some touchups, and I bought the cheaper contractor grade stuff. It was terrible. It might as well have been those water colors we all used as kids. It took four or five coats in some places to cover. Definitely wouldn't recommend it.