All NTA customers under active maintenance,
NTA v4.0 Release Candidate 4 should be in your portal now. RC versions are upgradeable and fully supported in your production environment.
The basics about NTA 4.0 are here.
Please make sure to review the FAQ here, especially the last section "FAQ on Installing a Release Candidate - RC - version of NTA 4.0" towards the end.
We cannot stress enough that following the deployment and platform requirements, is critical to get the performance benefits that come with NTA 4.0. Failing to do so may result in actually decreasing your NTA performances.
Please post your feedback about RC4 here
We really appreciate your involvement in the SolarWinds products and are looking forward to reading your feedback on NTA 4.0 RC4!