oo defrag also allows background defrag, on physical drives, so defrag won`t take another 6 hours +, but you can disable it when you launch set programs etc
defrag by name, and all the need for speed 2 min pauses when turning corners will be gone
Fragmentation of ext2-3-4 do happen as you approach the capacity of the drive, but since there are space reserved for such cases, you feel it a lot(!) later then on dumber filesystems (like on FAT for example).