As far as steaks go, and that's the only reason we ever go there, it's about as good as any of the "major" steakhouses in Las Vegas. It seems always fairly crowded, but when we want a good steak and don't want to drive to The Palm or Morton's (which is almost never for me), Fleming's is great.
I can't vouch for the Wine Bar, however, as I only drink "scotch" wine. Give it try, pricey, but good. Can't vouch for "Happy Hour" either, never been at that time. How uncivilized.
I'm not sure what "dressy" means, but leave your fanny packs at home and look nice.