IEEE 802.11a is nothing new, it's an old protocol dated from 1999 but running on 5GHz.
But since they like to make everything backward compatible, as soon they have the 802.11n on 5GHz, they also include the 802.11a.
(To bug more, the next standard is 802.11ac and will be exclusively on 5GHz.)
The One S don't seem to have the 5GHz enabled, but it's a design choice by HTC as the Snapdragon S4 support the 802.11a/b/g/n 2.4/5GHz (according to Wikipedia)
Google Nexus 4 16GB
Secondary: MyTouch 4G (Glacier) - iPhone 4 32GB
HP TM2T Win7/8 Convertible
Monster Beats Solo HD - Patriot Gauntlet Node 320GB Wifi mobile disk
4. HTC One S (screen shattered after a 2' fall face-down on asphalt)
3. LG G2x (P999) (didn't receive all call)
2. HTC MyTouch 4G (the HP jack broke)
1. HTC Nexus One (random rebooting + others issues...)