Trip to Oman

Driving over the border to Dubai requires cross-border insurance for the UAE, which costs quite a lot more and is only offered by a few rental companies, Budget was one was one I remember. Buses are pretty much direct Muscat - Dubai only.

Your trips sounds good otherwise, Wadi Ghul is a middle east highlight, and Nizwa fort is nice to see. The wadi Bawn Awf route is strictly 4wd only, and for people experienced driving on steep, rough, gravel roads. No need to do tours from Muscat, the countryside is the best place to be in Oman, although accommodation is limited, a lot of people camp. Driving on the main roads is completely fine, the road are better than most western countries.

You might find these posts useful on taking a car across borders, and general info on Oman, as I did a similar trip to what you want to do, camping out from a hire 4wd car.

http://www.lonelyplanet.com/thorntree/thread.jspa?threadID=2198138
http://www.lonelyplanet.com/thorntree/thread.jspa?threadID=2174493

Thanks SO much for all the help!

SSS

I had a Toyota Corolla for my first 3 yrs here and I went EVERYWHERE. So driving is easy. HOWEVER, the drivers here are crazy (2nd highest traffic fatality rate in the world!), so a larger car is better. Looking at your itinerary, you only need a 4WD for Jabal Shams and Jabal Akhdhar...........although you really don't. But there are a couple of check points where they turn non-4WDs back.
The highways are good, go everywhere, and are well maintained. If you go to a desert camp in Wahiba Sands (Sharkiya), you can pay the extra to have the camp pick you up at the highway and drive you in. It will save you a ton of money over renting a 4WD for your whole stay. (I do this because I don't want to mess with using my small 4WD on the unknown desert there. Okay, I'm a baby.) Besides, CARDINAL RULE: you NEVER EVER EVER drive ANYWHERE ALONE if you're going on the sand. ALWAYS go in vehicle pairs. (A couple of European women were recently saved by total luck in the UAE: their 4WD got stuck in the desert there ---- and only because the military was doing maneuvers were they seen from the planes the military were using. They would have been dead the next day from the heat and lack of water.......another thing to always keep plenty of with you.)
Re: the border ---- no problem if you have a UK or US passport.......or any number of other similar countries' passports.
Check out Lonely Planet for trip planning.
Have a super time! It's well worth the visit! (Please wear modest clothing to respect the culture here.....especially in the out-of-Muscat areas you'll be visiting. We don't need any more bad press for expanding tourism here!)

I agree with your last comment, I was a little disappointed to see women sunbathing in bikinis when visiting Wadi Tiwi, its really out of touch with the local culture. Rest of the advice is good too..