Recs.
Updated
Sentry is a log aggregation tool that really shines when paired with applications that have the mentality that any log message at or above warning requires human attention. It can be thought of as a replacement to automated emails from syslog.
Sentry was conceived in 2010 at Disqus and got the first paying customer in February 2012.
It supports many way to report issues which get aggregated and only "new" issues are reported.
SpecsUpdate
Pros
Pro Consolidates similar errors and makes resolution easy
It's what Sentry calls [Rollups](https://docs.sentry.io/learn/rollups/]. All individual issues rolled-up can still be drilled down. Also two issues can be merged manually.
Pro Has an official Docker image
Sentry has an official Docker image which means it's likely going to be well reviewed and maintained for a while and it makes it easy to set up.
Pro Completely open source, with a hosted version available
Sentry is a completely open source tool. It's free to use if you want to run it on your own. If you want to avoid the overhead of running and maintaining another server, it also has a hosted version available at www.getsentry.com
Cons
Con Can't filter by browser versions
Sentry only filters by browser names and not by browser versions (for example: Firefox, instead of Firefox 27, Firefox 28 etc...)
Con No free cloud hosting
Unfortunately there is no free plan for cloud hosted solution. Only self-hosted solutions are free to use.