I'm not saying Arduino is "bad", I just have gripes about the design. The ONLY reason I use Arduino is because of the great GCC support.
The boards, at the very least, should have usable mounting holes. People actually do build REAL projects with Arduino boards and it's ridiculous to either need special plastic standoffs or double sided foam tape to mount the board!
And, the Atmel AVR line certainly isn't the best choice for a microcontroller, but it's good enough for most uses.
I personally prefer the "Motorola" style (von Neumann) CPU architecture. The Harvard / Intel / AVR style architecture is a nightmare to work with. Thankfully, the C libraries shield me from most of that grief...