Went to my local Apple store today and played with the 5C. The fit and finish seems up to Apple standards.
Will it crack? Who knows, but it doesn't feel anymore sturdy or solid than other plastic phones.
And as mentioned by others, I found it extremely slippery. I'm really surprised that Apple would make it this slippery as given the colored shell, I'm guessing that many will not rock a case with this phone.
Wow I had a completely different impression. Didn't feel that slippery and definitely felt better than some of the Android plastic phones I've seen. Almost felt like ceramic to me.