What do people like?

• Reputation of JetBrains
• .NET platform support (MS Visual Studio integration and .NET platform build runners)
• multiplatform Build Grid
• completely web-based user interface
• industry-wide Version Control Systems Support (Subversion, Perforce, CVS, Visual SourceSafe, Team Foundation Server)

Key differentiators (according to JetBrains)

They've conveniently created a comparison matrix for TeamCity against CruiseControl and CruiseControl.NET.

• Build Grid
• ability to take responsibility for a build failure
• built-in code coverage (for Ant) and code quality analysis
• server-side search for code duplicates
• building projects from the command line
• IDE integration (IntelliJ IDEA, MS Visual Studio, and Eclipse (with Subclipse))
• Remote run of personal builds
• Pre-tested commit to keep the error-free code in the project database
• dependent builds triggering and possibility to set up the artifact dependencies
• Web-based file diffs
• LDAP authentication integration
• flexible notification rules and means of monitoring (web UI, IDE notifications, Jabber/XMPP protocol, e-mail)
• Windows Tray Notifier
• Third-party reporting tools integration and pluggable architecture
• Integration with bug tracking systems

Comments

• Reputation of JetBrains seems to be a significant factor
• Visual Studio support makes this a competitor for both CruiseControl and CruiseControl.NET
• Some of the features would normally be considered the responsibility of the build file but JetBrains understandably emphasises a more integrated experience with the IDE.
• Pricing:
  • $199 per user account on the server