"I'm slightly wary of a free lite version, at least at first, as people who get things for free tend to be more inclined to leave a bad review."

If someone were to take his/her time to post a review - it has to be something very extreme - either should absolutely hate the app or really love it. From the reviews I have seen on the app store, it's actually people who paid for an app and didn't like it who make a fuss..

I guess at the end of the day, there is no easy way about this. If you want leads, you need to either have a free version which will allow more people to try it and hence convert, or else put in the advertising to go for the paid customers. It's a situation that's quite similar to what I am facing too, but there is no easy way out of it. The viral loop doesn't occur always :)