Cisco IT migrated all of our mostly-Unix mainframe Oracle ERP apps to RHEL on UCS starting in 2010.
Moved our $48B/year "Quote to Cash" suite of apps from 4 Risc-based systems (running Oracle RAC 9i on HP-UX) to 4 UCS blade servers (running Oracle RAC 10g on RHEL) in 2011.
http://www.cisco.com/web/about/ciscoitatwork/data_center/qtc_erp_to_ucs.html

Moved our 40 TB Customer Care suite, one of the last of our Oracle suites, from 3 Superdomes (2 E10Ks, one E7K) to a 12-node Oracle RAC on 12 UCS blade servers on RHEL in 2012.
http://www.cisco.com/c/en/us/solutions/collateral/enterprise/cisco-on-cisco/Cisco_IT_Case_Study_C3_Migration.html

Migrating to UCS blades gave us better performance and lower power / space footprint. Most of all it gave us horizontal scaability - adding another blade is far easier than adding another mainframe.