The paid version of Robo Defense is probably the most used app on my Droid (other than Launcher Pro).
I am up to level 26 on "The Ruins". I've seen and defeated the Titan several times (it's really not that formidable), but I only got the Titan Achievement bonus the first time.
I've been playing a NE to SW diagonal zigzag pattern which handles the ground enemies fine but I need a new strategy against the most intense North to South aerial barrages where I rarely get a perfect score anymore. Just not enough real estate in the N/S direction to set up enough transporters to handle the worst barrages. Time to try something new I guess.
Am I an addict? I play it mainly on the can, but find myself spending way too much time on the can! It usually takes about 20 minutes to finish a level.
I just wish there was some more variety in the paid game. I guess that's what different layouts are supposed to provide, but still, the game could definitely use new weapons and new foes after the Titan.