OpenBSD 5.3 offers improved hardware support, including new driver. These new drivers are mostly for Ethernet/network, sensors, and disk controllers. There is also though some virtualization drivers via virtio, vio, vioblk, and viomb. Other drivers were also improved like AHCI and IX.
The OpenBSD 5.3 release also has networking stack improvements, SNMPv3 support, pf improvements, OpenSSH 6.2, and an assortment of other improvements and fixes.
More details on the new release can be found at OpenBSD.org.