The threshold actually was 4.5 percent, said Greg McBride, a senior financial analyst for Bankrate.com, because that enabled a lot of borrowers to save at least one half of one percentage point.

"When mortgage rates got below 41/2 percent, that opened the door for people who previously (refinanced) at 5 and 51/4 percent," he said. "Even at 43/4 percent, if you can snag a rate below 4, it makes sense."

Two, 15-year, fixed-rate loans are hot.

According to a report issued by Freddie Mac last month, of borrowers who refinanced during the year's second quarter, 37 percent went into a 15- or 20-year loan, the highest such share since 2003's third quarter.

The reason? It's not just about cutting the monthly payment anymore, mortgage professionals say.

"I think people are more conservative," said David Pendley, president of Avenue Mortgage. "They aren't looking for bigger and better. The mind-set is, 'I have to get my house paid off and shore up my finances because no one is going to do it for me.'"

Say a consumer takes out a fixed-rate, conventional 30-year, $100,000 mortgage at 4 percent. With a monthly payment of $477, that consumer is paying $172,000 over the life of the loan.

Shrink that loan term down to 15 years, at an interest rate of 3.25 percent, and it equates to a payment of $702 a month. Higher, yes, but over the life of the loan the consumer is paying only $126,000, or $46,000 less than would be paid on a 30-year loan at the higher interest rate.

"It depends on what you're trying to accomplish," said Ken Perlmutter, president of Perl Mortgage. "Do you want a lower payment? You want to go to a 30-year. If you're at a different point in your life and you want to accumulate wealth (a 15-year means), you're paying down the principal faster, you're building equity faster."

Three, no one expects a silver bullet to help all homeowners enjoy the low rates.

That means the same rules that applied at 5 percent still apply at 4 percent. For the best rate quotes, you've got to be pristine on paper and the higher the consumer's credit score over 700, the better. Homeowners should use the weekly rates announcements from Freddie Mac and the Mortgage Bankers Association as a guide only because they are dated by the time they are announced. Also, the rate quoted to a homeowner will also move up slightly higher if the borrower rolls the closing costs into the loan.

Homeowners also have to have sufficient equity in their home to refinance, and that level may not be the same as it was the last time they refinanced. The size of home price declines may have moderated a bit, but they are still trending downward.

In its most recently monthly report, the Illinois Association of Realtors said August home prices fell 10.4 percent from a year ago for the Chicago area as a whole and were down 3.8 percent within the city of Chicago.

That does little to help underwater or financially stretched consumers who have higher rates and would greatly benefit from a refinancing. Either their homes are appraising too low, or their creditworthiness is such that the extra fees required to get the loan don't make the transaction financially advantageous. Lending experts don't expect that the federal government will conceive any mass refinancing program to help all of those borrowers. After all, that was the goal of the voluntary Home Affordable Refinance Program, which has not met expectations.

The good news, according to loan officers, is that it's easier to get holders of second liens, such as for a home equity loan, to sign off on the subordination agreements necessary to refinance a principal mortgage in which there is also a line of credit. Getting that agreement may take a while, but they are getting done.