I'd look to transaction count relative to number of addresses. While it is possible they could move in tandem due to independent factors, it is somewhat unlikely. So far it looks like both point to increased usage, and anecdotal factors (bitpay/coinbase signups) seem to support that. The rate of growth is modest though, in line with historical trends rather than accelerating.
The network value factor lends the price attractor its parabolic progress during linear network expansion. Anything which is not a decline in adoption rate is massively bullish in the long run. Just a matter of time.
May I kindly suggest Nokia (Symbian) and Apple (iOS) didn't prove that installed base network effects in 2008 were unassailable. Android was a paradigm shift. The smartphone market battle is over given Android is approaching 80% market share and a billion users. The crypto-currency market battle has only just begun. It appears possible the same category of weakness may exist for Bitcoin et al, as did for iOS and Symbian; they may not be optimally open ecosystems thus scale less than optimally. I can't state this with certainty, but it is something worth pondering.
