Inflation and deflation aren't "controlled" by Bitcoin's design. The money supply is. Because the money supply is capped, over the long term, deflation is predictable.

The week-to-week reality of Bitcoin is one of wild swings in the "valuation" of the Bitcoin "asset". Describing these swings as "inflationary" and "deflationary" dignifies Bitcoin. Was the collapse of PETS.COM and resulting devaluation of its stock "inflationary"? Was its run-up "deflationary"?

That would solve one problem, although it seems impossible to pick the right level of inflation. Then we could get on to discussing Bitcoin's other problems, such as slow transaction clearing and poor usability.