Released by VMware earlier this month was VMware Fusion 6.0 and VMware Workstation 10. If you're running a new Haswell-based MacBook with VMware Fusion, you can expect some noticeable performance improvements by upgrading.
Shortly after the VMware Fusion 6.0 release I ran some early Linux virtualization benchmarks of Ubuntu on the guest and OS X as the host from my Retina MacBook Pro that I use as my main production system. There wasn't too much to see in that configuration. However, for VMware Fusion 6 on the Haswell-based 2013 MacBook Air, the improvements are much more noticeable.
From the new Haswell-based MacBook Air I ran some VMware Fusion 5.0 vs. 6.0 benchmarks. The host was the MD711LL/A model and sports an Intel Core i5 4250U "Haswell" processor with a base clock of 1.30GHz, 4GB of DDR3 system memory, a 120GB Apple SSD SD0128, Intel Haswell-ULT HD Graphics 5000, Intel Haswell audio, and Broadcom 802.11ac WiFi. OS X 10.8.5 was running on the hardware while the guest VM was a clean install of Ubuntu 13.04 x86_64 with no changes between running the 5.0 and 6.0 Fusion benchmarks.
A variety of benchmarks were carried out using the Phoronix Test Suite to compare the two releases. The Ubuntu VM had access to 2GB of system memory on the MacBook Air, 21GB of storage, access to all four CPU cores, and 3D acceleration support was enabled.