I've had issues with upgrades but only when the dates were not flexible (on only one occasion).. and was during a very in demand season (certain weeks in may, etc)

However if there is some flexibility.. I've found that emirates is by far the easiest airline to get upgrades with.. call skywards for more info.. you may need to call back a couple times to get accurate info...as some at the call center are unwilling to share all information necessary.

usually they will tell you if there are 1-4 seats available.. or 9+ i usually book early and shoot for 9+ so i can get as close to the front as possible and window seats.

if you want to do everything online.. just call before hand and get some info from the skywards rep.