OSNews has a pointer to this Ars Technica review of OS 4:
http://arstechnica.com/reviews/os/amigaos4.arsAt least to me, it seems to capture the "Amiga spirit" as well as review the OS.
Although the author is much too tactful to write "promises, promises" and "liar, liar, pants on fire", he does make the point about new hardware needing to follow. I sure hope that includes a card for my A3000D, but I'm too old to hold my breath. :-)