Intel published a white paper last year about a trial deployment of 802.11a as a replacement for wired Ethernet at a 5,000 person campus. The results were lower costs and happier workers. This was just for PC connectivity. The dual-mode phone phase of the deployment is still to come.
There are several interesting findings in the white paper. First, while the latency of the network increased somewhat, the difference was imperceptible to the users. Second, Intel chose to abandon the VPN, relying on 802.11i for security. This made joining the network faster and easier.
The decision to use 802.11a was presumably for the greater capacity (more non-interfering channels than 11g), and for the cleaner spectrum. 802.11n is superior to 802.11a in capacity and rate at range. This means that what was doable with 11a will be even easier with 11n.