Two things I didn't see mentioned, but I read perfunc., is the downside risk you run on the bond market decline (rate increase), and the difference between Money Market Mutual Fund and Money Market Account.

On the first, the shorter, and higher quality, your bond issue the less you'll be subject to principal +/- movement, but you'll be subject to movement, and considering the econ. environ. I'd say to - movement. So, consider that.

MMMF vs. MMA = you typically see different firms, ING/eTrade/whoever pay higher rates on their MMA. The difference is that while they both have to hold debt obligations with less thatn (I believe) 90-180 days maturities (VRO/D etc.), one hold solely the obligations of one back and the other a broad diversified portfolio of securities. MMAs, as they pay higher rate, carry a higher risk also as they are pooled from the sole obligation of the issuing bank, or just one back. MMMF, the ones that have been around for years, represent a more diversified port. And, that's why you get, most times, limited transaction activities on your MMA vs. the MMMF and that's also a way to find out what kind of a money market instrument you're buying.

Good luck!