ESXi is excellent, I think one of the best x86 kernels in existence. The management software is nowhere near on par with it; it is finicky Windows software that doesn't match the hypervisor's speed or reliability. The long-rumoured Linux version of the management platform still has not materialised.
The Linux version of vCenter is part of vSphere 5. There's also a cross platform version of the vSphere client, though it's written in Adobe Flex, so who knows how good that'll be..
ESXi is excellent, I think one of the best x86 kernels in existence. The management software is nowhere near on par with it; it is finicky Windows software that doesn't match the hypervisor's speed or reliability. The long-rumoured Linux version of the management platform still has not materialised.