Howdy, I left there a year ago now however made the odd visit back and things haven't changed too much.
Oman is one of the more expensive Gulf states but the offset to that is it is the most beautiful and the locals are wonderful people.
During summer your eectricity bills with 4 wall unit A/C's will be in the order of 60-80 Rials ($US 150-200). Winter is at least half or less than that.
The telephone company (as with many in this region) is a state run monopoly so is quite expensive, however they are deregulating so this will improve. Call to Australia ranges from 500 Baiza - 1 Rial a minute ($US1.30-2.60) for example.
Beers down the pub are on average $US5 for a pint (cheaper at the taxi bars but not the coolest place to hang out at!).
A night out with Wiffo and Kids at any of the premium hotels won't be cheap unless you go on a promotion night. A good night out for two adults with wines/beers etc. will cost in the order of 20-40 Rials ($US 50-100) depending on where you end up. If you just want some local nosh from down the corner shwarmer stand then you could feed the whole family for 10 bucks! A whole roaster chicken with extra's will cost about $3, cheaper than you can buy it frozen down at the expat supermarket!
I was in a brand new 3 bedroom apartment right in the middle of town for 300 Rials ($US800 approx) per month and all utilities (except power) never came to more than $US40 p/m. Villa's really depend on where you are in town. A three bedroom villa will range from 300-500 Rials ($US300-1300) in the outer areas and will increase in the premium locations.
If you want high speed internet the best at the moment is ISDN and only in certain areas. It is reasonably expensive but really worth it as the fixed line service is marginal to average at best depending on where you are in town. ADSL is becoming more available to the general public. Up until I left arranging any utility was a shambles to say the least...disconnecting was even worse! Hopefully things have improved.
Can't help you with schooling as I haven't owned up to any children at this stage!
Maybe
Diving Duck can add to this??!
Anyway hope that gets you started. Oman is a spectacular country and certainly the pick in the Middle East for a family, single social scene is a bit grim so I had to head west!
Good luck.
