Although this isn't specifically what I'm doing, it is in an indirect way.
This past Friday, I applied/locked in to refinance a 20 year, 4.99% Pen Fed Home Equity Loan with the Pen Fed 30 year, 5/5 ARM at 3.375% (with 1/8 point, no closing costs). I fully intend to have the house paid off by year 10, largely from cashing in some savings bonds that reach final maturity each year over the next several years.
After 5 years, the ARM resets the rate once every 5 years, and can only increase the rate by a max of 2.00% each time...so worst-case scenario is my mortgage rate will be 3.375% years 1-5, and 5.375% years 6-10.
My monthly payment will drop from $1,240 to about $880. I'm debating on what to do with the excess cash flow (since I already max out all available tax advantage accounts)...I'm pretty sure I'm not going to pay anything off early in years 1-5, but don't know if I should redeploy the cash in a Vanguard fund or individual dividend payers or what. My pipeline MLPs have risen nicely, and still might have some room to run, but have also been agonizing over whether to take the gains or simply leave them there and collect the 6%+ tax-advantage distributions.
As the savings bonds mature in 2011 through 2016, there will be a significant tax bite, but after taxes, they will account for roughly 80% of the mortgage principal.
I have substantial assets to where I can afford to take the risk with investing the extra $400/month; also, I like the added bonus of having the potential of having a 'reasonable rate' mortgage in years 10-15 if somehow rates stay low/fall again (surely not counting on it, though) and simply continue making bi-weekly mortgage payments with letting the money ride - although, if rates are this low 10 years from now, it likely means the economy is in the crapper, and there likely won't be many attractive investment options (not to mention that my entire portfolio would likely be down).
Now that I think about it, perhaps I'll be re-evaluating the paydown option in year 6....