I wouldn't necessarily consider that a warning sign. Generally, the only time people give a review is when something negative happens with their host, or there is a problem. Most people in the real world, running real world businesses, for example, don't go out and write huge, raving, detailed reviews about their hosts, unless they're asked to do so, paid to do so, given extra services to do so, etc. Most clients don't even know about sites like this.
We have been in business for 16 years, for example, with thousands of clients over that time period, and you'll be hard-pressed to find a good review out there. You'll also be hard-pressed to find a bad review.
Since you're looking for a free host, it never hurts to give them a try and see what happens. If you aren't satisfied in the first few weeks, it's really easy to move elsewhere.