Slow to start, 90% coverage for my test
Too slow often, other times quite quick - The slowness is my biggest reason for the 4 stars instead of 5. The usage is extremely easy, the result format is simple.
If you hit system hard to test you get 500 errors but with very low CPU load, it pauses often and perhaps is parsing another local area, but it doesn't do this on start - Just the first time you query an address is my guess (no details available).
With some improvement, especially in consistency of speed, this could be a much better solution.
A trick we have discovered with EC2, it to start the instance, leave it running for a few minutes then reboot. The second time it comes up it will be much faster. I suppose it has to do with the way AWS prioritizes EBS