As you state, there are benefits of saving, something that modern economics overlooks. Saving is prudent for most people. It allows capital accumulation, something necessary for future investment.
The current economy, based on inflation, forces everyone to speculate. Even at 2% inflation, in a generation, savings are cut by half. Why save?
The problem is not everyone is cut out to be a speculator. Only a select few are. Speculation should be their domain, not the domain of everyone.
The balance between saving and spending should be determined by a free market interest rate. Unfortunately, none exists today.
In a bitcoin economy, the value of money would grow with time. Only those who are cut out for speculating and investing would do so. The average joe would be content to save, and they would be able to capture the growth of the economy through the rise in the value of bitcoins, not through speculation.
I just got this real crazy idea.
What if Bitcoin encourages people to stop spending more than they need to buy? Since by holding BTC you're likely to become wealthier, thereby decreasing the need to spend frivolously, people would hold onto their coins and spend them only when they had to, such as for food, shelter, and the recurring payments of entertainment--and everything else would be only if they really mean to spend, as on their business ventures or schooling or whatever else. On the other hand, with fiat, you're encouraged to get rid of it ASAP on whatever it is you need or want. Capitalism seems to favor an inflating currency, as people are more likely to get rid of their cash by either buying or investing in something else (but average Joe seems to prefer to buy.) Therefor, more money runs around, the economy (is supposed to) keep moving, la-de-da.
I think a society that's more focused on conserving their cash (and thus, their resources) is much better off than the society that must eternally spend and expand. Maybe people won't waste their hard-earned money so quickly then, and won't be so easy to coerce into giving a bank for gambling purposes--I mean, investing. This system seemed to work well when we needed to spend and expand, but now that phase is over, and the cup keeps spilling over.