I'm a frequent One World flier, this was my first time on Qatar. Connecting from an AA flight from Philly to a Qatar flight to HCMC.
I heard only good things about the airline. It is supposedly one of the better ones in the world. All that may be true if you fly in one of their Qsuites.
This flight was in a 777, seats were more like lounge chairs than fully lie-flat beds, very cramped feel for a business class, window seats, my preference, had no direct aisle access - you had to climb over the person next to you with acrobatic skills. Service was good, so was the food, but if you stretched out your elbow, you would hit the passenger next to you.
My advice - do not fly this airline in business unless your flight offers the upgraded Qsuite. If not, this is nothing more than a budget business class experience; except for the food and service, which were very good.
One plus - if your layover is around 6 hours (or more), Qatar offers a 3 hour Doha City Tour. It is easy to exit the airport, and if flying business, they have a fancy business/first check-in area, with dedicated immigration and security lines, so the return to the lounge or gate is a quick no-lines experience....and the City Tour, if you've never been to Doha, is a fun and worthwhile experience. The business lounge is fancy, nice shower rooms (may not be available if you fly on a code share), but when it comes to the food offerings, I was expecting a more 5 Star experience. In fact, it was no different than most any other lounge.