The N54 is award winning (2x international engine of the year awards and 3x best in class). If it wasn't for the HPFP, I think it would be the climax of BMW's inline 6...(I think even better than the S54 that comes from the NA e46 M3)
http://en.wikipedia.org/wiki/Interna...ne_of_the_Year
The N52 is great, and more reliable, but that N54 is so torquey, tunable (400hp? easy), and fun imo.