Veeam is one of the first backup solutions supporting vSphere 5.5 (take a look at my support matrix for backup solutions/vSphere 5.5).
With the latest patch (build 7.0.0.764) Veeam Backup & Replication v7 is now supporting vSphere 5.5, vCloud Director 5.5, Windows 8.1 and Windows Server 2012 R2, too!
To learn more about this patch take a look in the Release Note (KB 1831)