82 degrees and change is the average wild reef temp. Some get up to around 85 and the most biologically diverse reefs do tend to be the ones that are at or near 85 degrees. When I had my reef tank it was almost entirely sps and I would keep it at around 82 with dips down to 78 at night. You will get faster growth at higher temps as long as your parameters are in line because the temp does act like a dial for the metabolism of the fish and inverts. Calcification does become much faster as well so skeletal growth becomes far less dense at higher temps and they can become brittle. LPS don't have to be as high since most come from greater depth than the SPS species.
There are other factors to consider like electrical usage at higher temps, more dosing of calcium and alk. additives as well as trace elements to keep up with the demand, the needs of certain livestock that might not be able or rather, shouldn't be exposed to higher temps, etc. It's best to keep the swings to a minimum and use the heaters to maintain a temp just below what the tank gets up to during the day if you don't use a chiller (which in my opinion is one of the most over used and potentially problem causing pieces of equipment out there).
You also want to consider the extremes. If we consider 85 as being the "high" end than you are going to want to give yourself a little breathing room and keep it down just in case. There is a max temp at which point the livestock can no longer stand it. I'm not sure what that point is but what claims most tanks that "overheat" is in fact the speed at which the change occurrs. For instance, a 4 degree change over the course of an entire day isn't going to do much damage but when you take that change and make it happen over the course of an hour, things are going to die even if that 4 degree difference is within the acceptable range.