Shrug, my gen one is the best phone I've ever owned easy. Smokes my Nexus 4, even considering I jumped from an awful Samsung Charge. 
Yes there is a real upgrade going from Vanilla Android to CyanogenMod IMO.
Lots of risk (lack of support), but reaping the rewards of a great phone for half the price of comparable phones. 
I love my nexus 5- don't plan on dumping it anytime soon.
