Well you can always just pay down the principal, right now every dollar I put down on my principal I save a dollar in interest. Paying 10 grand on my principal right now will save me 9,700 in interest in the next 3 years. Where can you make that kind of investment, 100% in 3 years???
As for PMI, mine was 45 a month which really annoyed me. So I just payed down my principal to eliminate it. I dont know how you get away with buying a house without it, but all loans are different and mine required I have it until I was like had a percentage of the purchase price paid off. I couldnt even get my house reappraised to get rid of PMI because of the loan that I had.