Modification/Early payoff...we're back on track now BUT about $70k upside down!!!

After all that work of trying to get a modification (which is great;don't get me wrong;we get to stay in our home), we have another dilema which is being upside down with the values of today's market. It will take us several years before we accumulate equity. Just some venting I am doing; I guess. I have had someone approach me regarding paying down our mortgage thru a company that cuts down the payoff time in half or even to 1/3. In other words, paying off your mortgage in as little as 10 yrs! Can anyone (who is actually using this system) tell me or warn me of anything regarding this program. This is also an MLM (surprise, surprise) and have been approached about by a few people. It's a wonderful program in theory but, I need to know of someone else (other than the person trying to sponsor me) tell me what horror stories or experiences they have found out about this system. Thanks, Liz