For those who like me have been looking for a replacement card for a MacPro 1.1 (2007), here is the solution. The card works in my MacPro 1.1 (Dual-Core Intel Xeon, 2.66GHz) without any problems. The installation was not difficult, despite the length of the GK. The fan is very quiet and listen, even under load hardly, I have ever seen in the case if it runs at all ;-). Under Boot Camp Windows XP with latest ATI Radeon HD5770 drivers which also works excellently. Recent games run with me with 1920x1200 (DX 9c) very good, although not all graphics features are supported (through XP).
Conclusion: the card is a recommendation, if like me an old Geforce 8800GT is smoked (by 2008).
Drawback: the price is a bit high like Apple, but worth it anyway.