Being an Oceanic player on a US time-based server (Proudmoore) rather than an Oceanic time-based server (such as my main Horde server, Frostmourne) has a lot of advantages:
The best advantage is that at almost any time of day, there is a sizeable population online. The same can't be said for other servers (such as Nerzhul, where my main alt warlock is based), where you can /who Dalaran at certain times of day and not have a full 49 listed. The population advantage (as well as the carebear PvE status) helped Proudmoore grind SSO dailies like no other, winning the race to each Sunwell phase.
It also helps with PuGging, particularly retro raiding, as there is both a US and Oceanic population to pool interested parties from. MC, BWL, AQ40 (it took quite awhile to find a group that could get past Twin Emps!), SSC, TK, and BT were all PuGged extensively for one reason or another, and I'd still like to get Hyjal and Sunwell completely cleared at some point too.
However, being on a different clock to server time has a lot of disadvantages, too:
I have never been able to compete in the STV Fishing Contest, as Sunday afternoon for the Yankees is Monday morning for Oceania.
Rolling restarts on Proudmoore still happen between 8-11pm on Tuesday nights, unlike Oceanic servers such as Frostmourne, where (if you're lucky!) Blizzard will sometimes push back rolling restarts to non-peak times (ie 5am AEST, not US time).
...and something I wasn't even aware of until recently - we miss being able to turn on the lights in Dalaran at 9pm server time.
I know these things are such a small part of WoW, but I'd still like to experience them. Oh well, maybe one day!