If you read the reviews here, you'll conclude that sh404URL is a mature and technically strong extension. I've used on 1.5 and 2.5 sites: it works well, it's easy to use, powerful and it performs well. But it changes Joomla a bit and some people run into problems requiring support. I recently became one of these. First line support was fast in responding but we had difficulty mutually comunicating what the issue was. I was getting very frustrated, so I called. The phone was answered very quickly and with the help of customer service my issue was resolved & it was only a configuration problem.
I have to say that initially the support request was not handled well, but the effort to get on top of the problem via my escalation was extremely customer-centred. You can learn a lot about a team not by the mistakes they make, but how they deal with them. I continue to be a happy subscriber.