Infoworld reviews X4150

Paul Venezia of Infoworld tested the Sun Fire X4150 and was quite pleased with the performance - Lab test: Sun’s X4150 shows the beef:

All in all, it's a very real competitor to HP's ProLiant DL360 G5, IBM's x3550, and Dell's PowerEdge 1950 III. In fact, the fit and finish of the X4150 are generally better than the rest of the field's and far ahead in local storage.
The X4150 is priced similarly to other servers of comparable spec, yet offers storage and I/O capabilities generally found in 2U and larger systems – this not only saves on rack space, but given the relatively low power consumption of the X4150, it can save on power as well.
The most suitable roles for the Sun Fire X4150 will be in database, Web serving, and virtualization tasks. In these spaces, the X4150 provides significant bang for the buck in nearly all respects