The one potential downside of this is that it reduces incentive to invest in growth. If your Bitcoins will increase in value just from holding them, then the return from an investment has to be that much higher to make the risk worth it. But that may be an old world way of looking at investments. People on Kickstarter and Kiva and sites like that choose to invest in things they want to see created, not in things that give them a financial return. Maybe that's the way investment should work.
While I don't believe inflation is needed and good, nor that more consumption is usually a good thing, I do see reduced investment as a probable economic outcome (probably less bubbles too though, except for the big bitcoin bubble that is bound to happen if the systems manages to survive all hurdles :-), still orders of magnitude away though). The degree to which this will have a negative impact on the economy will depend on the rate of deflation (since investments need to produce at least that percentage of profit, and then some).
I don't agree with the idea that people will suddenly look at investments in a different light, maybe some idealists will, but this will never be more than a minority. I don't see why there would be more of these types of lending than is currently being done. The majority of lending practices will still be about making money.
Back to my original point, it seems to me that the nature of Bitcoins encourages people to make better life decisions for themselves. It encourages people to save instead of consume. I'm not saying don't spend Bitcoins. Let's get this economy booming. But we should also celebrate, not being frustrated by, the fact that Bitcoins don't encourage us to act against our own self interest the way other currencies do.
Couldnt agree with you more.