I wouldn't buy the slim because I have a 1st gen model with PS2 H-BC, but the 1st gen version is definitely the ugliest and bulkiest system ever. The only system that comes close to that is a 1st gen Genesis with a 1st gen Sega CD and the 32x attachment. I think this slim look is a slight improvement.
For Sony, I think a slim model would be an excellent marketing and economic move.
Now, I wish MS would slim down its system. I would buy a Slim 360 without a second thought.