I purchased a blue 2005 Ninja 250 on July 6, 2012. My previous motorcycle was a CBR125.
I must admit, I am a little intimidated by the Ninja. I know I just need to ride it more to get used to it. I do miss the FI of the 125. But, I am getting used to the choke. Oh, and I definitely miss having a fuel gauge.
I jumped from an 80cc scooter to my '07 EX250. Quite a jump, but easy to get used to. Nothing to be worried about at all if you don't ride like an idiot lol. Just be smart and defensive and you'll be fine.