Smoke detector at highest point of pitched ceiling - good or bad?
It's generally best to install smoke detectors up high where smoke will reach them as quickly as possible.  However according to the NFPA you may have some latitude, and you actually don't want them all the way at the apex of a peaked ceiling.  



source:  https://www.nfpa.org/Public-Education/By-topic/Smoke-alarms/Installing-and-maintaining-smoke-alarms

There are additional considerations for placement at the above link that should be reviewed if you decide to move your smoke detector.  

Keep in mind that that smoke detector may very well be required by local building codes, and you'd want to be careful that any changes you make are code compliant.