1. Old chipset
2. Unpopular chipset
-P45 was much cheaper and clocked slightly better
-X48's USP was 2 x 16x PCIe slots and current graphics cards don't really need more than 2 x 8x
- DDR3 only
3. It was overpriced to start off with.
4. It's a FoxConn - good luck getting RMA support once the initial retailer supported warranty period expires.
That said - as Gurusan has demonstrated, it's an awesome motherboard, especially with the new generation of ATI cards looking like they may be able to saturate 2 x 8x motherboards in CrossFireX.
It could be a very good buy if you have a known-good S775 CPU and are planning on going CrossFireX with the next ATI 5xx0 series cards in the near future.
Other than that, get a P55 or X58 board if you're starting from scratch.