I just started 2 or 3 months ago, and it is tons of fun. I have been working on little things for it here and there almost every day, so I haven't even been playing video games much at all. I started with Diecimila and also got a DC Boarduino a few days ago. I was thinking of getting a Nano, but lack of built-in DC jack swung me towards the Boarduino instead. Pretty nice since it is only around 1/3 the cost of a Nano.
I love the environment, it was super easy to learn. I was very intimidated by microcontroller programming, but picking this up took only a day. It's small, inexpensive, and so versatile. The only problem I can think of is that the programming environment is so high-level and easy, that the skill will not transfer well to programming other microcontrollers.
Here are some of my creations...

The first robot I made, it's pretty dumb. I also eventually ditched the 8xAA batteries for a 9V + 4xAA.

Pretty much all the same stuff as the first bot, migrated to a different chassis. The sonar rangefinder is mounted on a servo so it can navigate obstacles somewhat more intelligently.

Just got this working last night. No sensor yet, it just walks forward clumsily. I only have 4 good servos, the rest are not strong enough to support its own weight when I built each leg with 3 degrees of freedom, so I had to drop it down to 2DOF.
So I am mostly into making robots, but Arduino is so cool that you can do almost anything you can imagine. I plan to try making an autofire circuit with it sometime too so that I can improve my Mr.Driller game.
Let's see your stuff!