When 7th ed was first released, Unbound lists looked really overpowered, however now with the detachment systems in the last 4 codices(Necron, CW, SM, & DA), players can pretty much take whatever they want anyways, and in addition benefit from the detachment bonus rules.
For example in a regular Battle Forged list, Craftworld Eldar can legally field 12 fire prisms(Vaul Engine detachment), or 12 squads of fire dragons (Aspect Shrine detachment), and also get bonus rules too. Again, this is in a Battle Forged list, and this is the direction all future codex are headed.
So with that said, what are players opinions of unbound lists now? Especially with the "older" codices, are players worried about unbound orks or chaos marines anymore? Perhaps the Unbound list was always intended as a failsafe against future codex creep. Thoughts?