Not very. Right now, liquidity preference and risk aversion is at my lifetime high so it makes sense that everybody wants to park their money in the safest, most liquid place they can think of. Treasuries and T-bonds are sold at a discount, meaning the U.S. government agrees to pay out $100,000 in 3 months, 1 year, 5 years, 10 years, etc. People bid for them, say, $99,000. So the $1,000 would be what they earn on the Treasury bill or bond, or 1/99=1.01%. Recently the U.S. government have people bidding $100,000 for a promise to pay $100,000 and sometimes a little more than $100,000 for a negative nominal return (not even counting inflation -- real returns would be even more negative if inflation is positive).
But:
The oil-producing countries and China have parked hundreds of billions of dollars in U.S. Treasuries, bonds, etc. The former are reeling from oil prices tanking and China is experiencing a fall in exports for the first time in probably 3 decades. Both of these countries might start selling treasuries to keep their own economies from falling into a serious recession. With the U.S. government selling Treasuries to pay for its own stimulus plan and bailouts and a healthy sell-off by the Saudis and Chinese, the prices should drop. As prices begin to drop, the speculators in Treasuries will get out too, increasing the rate of Treasuries' descent. This descent will probably be accompanied by the a relative devaluation of the U.S. dollar versus Euro, Yen, RMB.