You need both part 1 and 2 to get the certification from Sun. Until you get both, you aren't sertified and can't take the network or security certificans.
I passed Part 1 (310-011) last month and Part 2 (310-012) this month. After passing part 1, I didn't get anything from Sun. After passing part 2, I got a nice little certificate, a nice little pin, a little credit card like thing with my certification info on it, and a letter with a URL and instructions on where to get bitmaps of the certification logo to put on my business card and/or resume.
Hope this helps.