IR rework is a totally different ball game from hot air. It takes a while to get used to it. Many who complain about it not working are not willing to experiment and take time to learn the process. Many who are using the machine successfully don't bother to post their results here. If u search through old threads you will find people who are using the machine successfully.
Once the heater height is adjusted, its good for that particular type of job. Heater height has to be adjusted as per the type of job you are doing. For small BGAs like mobile ICs, you need more height as if you keep it too low it may heat too fast and burn the chip. For larger BGAs the height needs to be less. The closer the heater is to the item being heated, the more heat is transferred to it faster. Keep that in mind. You need to observe and use common sense. After a while you will develop a feel for the machine and just know what settings to use. Do watch all videos by Raheeeeb to learn how he uses it. He mostly uses it using manual controls. But you can make your own profiles by using the profile editor as shown by him. Once you have a profile, you can save it for future use.
The temperatures for reball and reflow are the same as solder being melted is the same.