I researched microloans during my studies of International Development in the early 00's, back when it was first becoming really big with Grameen Bank. My girlfriend has also had accounts with a local Danish
microloan-org - since 2007. Unfortunately they had to downgrade operations because a lot of the debtors could not return payments, but they are still in bizz.
There's been a lot of debate about the efficiency of microloans in recent years, much like the general debate on the impact development assistance and 'fair trade' (which we've also worked with for over a decade) and I suspect that the bottom line still is: sometimes it works, sometimes it doesn't. It depends a lot about circumstances.
A recent, very
thorough report from the national British development institution - DFID, their pendant to USAID - had a very skeptical conclusion about the impact of microcredit. I still believe that it works, under the right circumstances, and possibly coupled with other types of assistance/aid/reforms, but I have to admit I haven't kept up-to-date on the debate.
It's great, though that Steve has introduced this type of very personal way to assist people in less materially prosperous parts of the world (to put it mildly); - a way to help them cover their basic needs by becomin self-sufficient. That can only be a good thing.
But do check around before you commit to supporting any particular microloan initiative. Common sense, maybe - but still... it's easy to bet carried away. And no, I haven't heard anything negative about Kiva - it appears they are one of the major and more reputable players in the bizz.
But keep in mind, apropos the recent evaluations mentioned before, that the general positive impact of microcredit is still very much a contented issue.