Disadvantages of low introductory rates on balance transfers?

I'm a homeowner with no debt except my mortgage. We financed 90-10-10 (2nd loan = homeowners line of credit with an adj rate). That rate has climbed up to 7.5% and i'm always getting credit card offers for 0% APR for the first 6 - 12 months. Is there any good reason i shouldn't max 1 of these out to pay down my 2nd mortgage? Besides the obvious:
1. credit score? i'm not planning any big loans soon...
2. i could screw up and miss a payment and get hit with a big penalty
3. i might forget that i am not rich and start spending my entire loc until my credit is so hosed i can't tranfer my balance elsewhere.
4. tranfer fees. The cards i'm looking at charge 3%, but with a max of $75 so that is peanuts compared to my interest savings.

Is this not the easiest way for me to save a grand this year? I figure when the intro expires, i'll rotate the balance to another 0% intro as long as i can qualify and drop back to my 2nd mortgage at ~7.5 as backup.

Seems like free money, what am i missing?

to be clear, i have NO intention of paying off the amount in 12 months or less. It will take more like 5 years. Putting it on a card is a temporary solution. I would definatly leave my loc at the bank open as the backup plan... thanks.

It can't hurt you as long as you know going in that the rate will change after the introductory period and you have the option available to move it back to the LOC later.

I did it once with a balloon payment I had on a note and I just paid as much as I could on it during the intro period and then when it converted over I owed less than $1,000 and had it paid off within a couple of months.

The only good reason is that if for some reason you are unable to pay off within the introductory time, I can almost guarantee you that the following rate will be significantly higher than 7.5%

First of all the equity line is adjustable to the prime rate. If I were you I would go to the bank and get a closed in or fixed rated second mortgage to replace the equity line second that you now have. Never transfer that kind of balance to a revolving card. That is what a Home Equity Line of Credit (HELOC) is. You at this point may only be paying just the interest on the note an 0 to the principal on the HELOC. The problem at even 0% interest on the credit card is you have to look at the fine print on the cards offer to see where the rate will adjust to after the 6 month intro period is done!

How long will the 0% last? If it's only 6 months it might make sense to use it for the equivalent of 6 months' worth of mortgage payments, but only if you discipline yourself to making payments on the card that are at least equal to your current monthly mortgage payments. What the credit card company is banking on is that you will get stuck with a high balance once the introductory rate expires. It's a sucker's trap that many people fall for.

You are playing credit card roulette....and you are going to lose.

Besides the arguments the others have given, and the points that you already know, you will now be making 2 payments. Can you afford that?

Personally, be very grateful you are not loaded with lots of debts, and put everything you have into that one home equity loan.

Also, everyone misses one thing. Your interest on the home equity loan is tax deductable. Credit cards are not.

the long term rate is probably higher than 7.5% on your HELOC and don't forget that the interest on your HELOC is usually tax deductable (consult your tax advisor) whereas credit card interest rate isn't tax deductable no matter how is was accumulated...also by continually transferring from one 0% to another you will continue to pay the transfer fees (although less than accumulated interst over the promo period) and have to have your credit pulled each time thus lowering your score and potentially limiting how many and how often you receive the 0% offers

You didn't say how long you've been in your home. Could it have appreciated enough for you to roll all your loans into a single fixed rate re-fi? This will keep your rate low(er than credit cards - there's no guarantee you'll be able to keep rolling the balance over).

Credit cards are REALLY dangerous. The overwhelming number one reason cited by most divorcing couples is financial trouble. It can really screw with you. Think carefully about this before making a move.