We've been using Timber in production for a while now at Exeq, and it's been mission critical to us. Having consolidated, searchable logging across our (5+) systems has been awesome. Love working with their team as well; they love feedback and take it very well. Their alerting is actually too verbose for our needs at times, but configurability is coming! Would highly recommend.
Timber has been core to our infrastructure since day 1. It's drastically better and easier to use than the competition. I highly recommend you give it a try, you won't regret it!
Switched over to timber months ago and it's been awesome to work in. Navigating to different times and filtering is really easy compared to Papertrail.
If you use Rails+Heroku (or any of the other stacks they have special integrations for) I'd highly recommend it, as there are a bunch of convenient features you get out of the box, like being able to easily query the logs of a specific user, etc
This isn't really a con, but their ruby/elixir library allows you to attach user context data to logs and I would love to be able to easily do that in my Python + Go apps. Otherwise love the service - have used a bunch of different logging service in the past and this by far one of the easier to use services