Quadband phones are a bit thin on the ground at the moment but I strongly recommend one. Just six months ago, 850Mhz coverage did not exist in the US, and now, more than a third of the country has either a combination of 850/1900Mhz GSM coverage or exclusively 850Mhz coverage. 850, as with 900Mhz offers much better building penetration and rural coverage. If your option is an 850/1900 phone for usage in the US and a 900/1800/1900 phone for usage abroad, I would go that route. You can find VERY inexpensive dual/tri-band GSM phones for use in the rest of the world... I wouldn't forego 900Mhz coverage.