We're starting to go in circles...
They are not minor problems... The USD volume (minus changebacks) is flat since April, and still less than January
USD tx is "flat" only from a very shallow analysis. Looking at it in more detail, we see it drastically fell from a peak value in December last year, with one intermediate spike in March, to a low point in May, and has been rising since then despite falling price.
USD tx going up since May despite falling price means one thing and one thing only: usage is going up since then. Sorry if that doesn't fit your narrative, but it's about as close to a fact as you can get, given our imperfect ways to observe the economic network size.
Yes, I will give the same spiel again. As I wrote before, adoption surely increased from 2012 to 2013 to 2014. But I do not see any clear signs that adoption has been increasing over the last year. The most germane indicators that you use as evidence of year-to-year increase show a decrease and stagnation since January.
Bitpay went from 5 million USD per month to 30 million per month from mid 2013 to mid 2014, and you're "not seeing any clear signs adoption is increasing". That's really pretty funny... Let me try to drive home my point that you're cherry picking now:
Is there a climatology department at your university? Maybe go over there in a year when the latest climate data does
not show an increase in average temperate or some other metric that is used in the global climate models, and tell them that it looks like climate change/global warming is over, since their latest data point doesn't show a continuation of the trend. See how they'll laugh as they you show you the door.
I'm being a bit facetious here, the Bitcoin market trend is less established (and less researched) than climate trends, but the principle is the same:
If there has been a strong, clear trend of about 5 years, you cannot conclude from a weaker subtrend of a few months that the larger trend has reversed. You can be "skeptical" perhaps based on the latest data points, but the global assessment still has to be driven by the global trend, not the local one.
I'll summarize:
Fact: Adoption is way up from 2010 (when the network went live on a global scale).
Fact: The latest available data that is indisputably in favor of growing adoption is from mid 2013 to mid 2014 (e.g. Bitpay).
Fact: The intra-2014 data is less conclusive, showing both signs of falling trends and rising trends.
Conclusion: If in one or two years from now, the numbers (like USD tx, Bitpay/Coinbase volume) are stagnant compared to now, we could perhaps conclude adoption halted. But as of December 2014, it is a safe conclusion, given the data, that adoption has been growing.