Britney Spears, Zoe Zaldana, Anston Mount, Dan Akroyd, Justin Long, Taryn Manning and Kim Cattrall. AND Shonda Rhimes (Greys Anatomy & Scandal) wrote the script! The movie is awesome. Honestly, a total chick flick. It's funny, sad, romantic, clever, musical, and it has an awesome roadtrip story. Why do people hate it? Because Britney Spears is in it. Well, if your gonna judge it based on that and not watch it, than you are REALLY missing out on a great movie. Besides, Britney does great in it. I bet if you're not a 100% Britney hater, you'll see that her acting abilities surprise you.
Do yourself a favor, and watch it already.