I was a bit disappointed that you could find secrets only while being at a specific point "time/place" and that you can not return to the begining of the level after beating it - that sux, but at least there were nice secrets at all and all of those artifacts made it look like an important thing to do besides bashing monsters.
And thank's alot to Bloodbuster and Greybeard for their dedicated work on NecroVision' secrets page! That helped alot, because i was really pissed off after beating some levels to find out that i missed something..
http://www.bloodbuster.co.uk/