I have been using defraggler for a while now and have been pretty happy with it so far, but when my page file became fragmented I was forced to turn to Diskeeper (trial install) since it seems that it is about the only defragmenter able to fix that issue for Windows 7. Will I was playing around with it I happened to notice that on drives that defraggler said there were no fragmented files Diskeeper often listed one or more fragmented files (and not files that were locked or otherwise inaccessable), which it was then able to defragment.
I realise that different software can have different criteria for certain things, but fragmentation would seem to be a fairly black and white issue (either a file is fragmented or it isn't).
For the record I'm using Windows 7 x64 with multiple SATA drives (2 data drives, 3 drives in RAID 0 - split into 2 partitions).
I can happily provide any more information needed!