Ok, saw on the web some guy going over the entire codex (on vid), not sure how legal is it to post it here.
However, holy hell stratgems are awesome, really pushes the whole "get CPs" thing, even beyond the fact relics costs CP.
Relics seems good, they are mostly just upgrades on top of regular gear (improved artificer armor, improved storm shield, improved flag, super chainsword, etc)
The fact one is free means you'll parctically always see one, the second relic costs 1CP so you'll likely see two, not sure about buying a third for 2CP though, CP are awesome, and flexible in their use mid-game, relics are more rigid and generally just give a numerical edge, rather than a tactical ability.
Unless you are raven guard, thier relic is freaking awesome (super jet pack, charge after running, and reroll charge range. you ARE getting there.)