I prefer to use TeamLab than other similar applications because it's easy-to-use CRM system and has well-integrated suite of tools.
Basecamp sets the standard for ease of use and also importantly in data sharing with other applications. It would even be better if they told developers when they change their API!
We have been using this for a few months now, with about 30 users. It works really well!
Asana is fantastic tool. But we will wait while they add time tracking in asana. For now we use excellent time tracking system in ProofHub (proofhub.com), its project management abilities are a bit simpler than in asana, but time tracking functionality is really good.