The first few times were cool. I ate better on the road than I did at home, had all my expenses paid for PLUS getting my regular pay, learned how to have a few beers covered on the expense report (technically, they are not reimbursable).
Then it quickly got to be a drag. Flying is a major hassle these days. If there's a delay you might not get to the hotel until after midnight - and still have to be wherever at 8AM. Maybe the hotel gave away your room - oh, if that happens they will pay for your first night at a different hotel, but it could be a lot less convenient place to stay. And you can't eat great meals every single night or you end up weighing 300 pounds. You don't have enough time to do things you'd like to do in a new city either.
Now for people who don't mind living on the road for extended periods of time, the money can be astronomical. We had a guy who worked for three years in a different city. They paid for his apartment, his rental car, and he got $45 a day to cover everything else (meals, laundry, phone calls, etc.). On top of that he got his full regular pay. Imagine how much more money you could have without rent or a car payment for three years. They also paid for him to come home on alternate weekends - and he struck a deal that he could use that money to travel somewhere else instead of home if he wanted (wasn't allowed to keep it though). So on weekends he'd fly to Toronto, Vegas, Orlando, wherever he wanted.