I don't work for China Airlines, but have decent knowledge of Taiwan and working there. It is possible that they will stop or curtail the F.O. hiring due to a new government policy. Not sure the status of that at the moment but there was some mention of it on Pprune.
I believe the pay being offered was in the $4000 per month range. Not sure what other additions to that might be in the package. The biggest one you would want to make sure of is a housing allowance if based in Taipei. $4000 per month won't get you far in Taipei so that relates directly to quality of life. If you get another $1000 to $1500 for housing then it would be adequate. A decent furnished two bedroom flat in central Taipei runs over $1000 per month. A three bedroom would be anywhere from $1200 to $2000. You can live out by the airport for less, but that wouldn't be much fun. You really need to live downtown to enjoy life there. I say furnished because un-furnished is very different from what our perceptions are in the States. Un-furnished in Taiwan means absolutely nothing included in the rental. You would have to buy an air-conditioning unit for every room, a refrigerator, etc.
If you have children then you would really need to live in Tienmu since it is close to the American School and that is even more expensive. That would almost require that you have a car as well, which is best avoided if possible. It is much more convenient to take taxis and ride the bus then own a car. You can always rent one if you want to do a day trip from Taipei.
So, I now have you living in the middle of a concrete jungle. Believe me it really feels that way on some days. To stay sane I used to go out to the edges of the city and hike on the Japanese built trails, usually leading to a Buddhist temple. It was a nice way of getting to see some green and breathe a little fresh air. If you golf then you could do that as well, roughly $100 for 18 holes. It isn't a very outdoor oriented society so indoor activities are more the norm

Lot so of good restaurants, movies in English, decent pubs, even decent cultural programs at the Performing Arts center. The center, southern, and eastern sides of the island are quite nice to visit and going into the mountains can be a lot of fun, but it isn't set up for English speakers.
Now that I have broached the language subject, lets go further. If you are flying at China Airlines and happen to be with two local pilots they will spend most of the trip chatting to each other in Mandarin. That might make you feel a little like an outsider, which you are by the way, or it could make you want to learn the language. This goes directly to your on the job enjoyment. The other part of the language issue is getting around in Taipei. None of the cab drivers speak English and very few of the shop owners do either. The only place you can get away with English is in western restaurants and big hotels. So you either learn the language or get an interpreter
Back to flying for China Airlines. I wouldn't want to be an F.O. in Asia. The CRM issues and cockpit gradient are not to my liking. I'm sure it is getting better, but what I witnessed as an instructor there was appaling. Captain's would literally slap the F.O.s hands away from the flight guidance panel if they didn't agree with what they were doing. Not that the F.O. was doing something wrong, just that it wasn't the way the captain would do it. I couldn't put up with that no matter what the pay was.
Upgrades for foreigners at China Airlines are probably illusions. They say 3 to 4 years from what I hear, and while that may actually happen for a few, I doubt it will continue. EVA is a good example. They would tell a guy 4 years and then you will upgrade during your second four year contract. Yet, they would keep pushing that number back. I know very many people who left EVA for that reason. China Airlines will be the same and the reason is that it is unfair to the local F.O.s who should be getting upgrades before you. You are just hired help filling in until the locals are qualified. They don't want you in their left seat.
Still interested ?
Typhoonpilot