Thank you for sticking with me.
The results of the guest user test are as follows:
Results were way faster than my regular account, but slower than my wife's mac (hers is a '15 air, mine is a '12 retina). It's hard to be certain, but I think it is slower than response under Yosemite. It was slower than response in safe mode.
Contents of Console are posted below, notable is the absence of the _XPC connection was invalidated_ message.
The results of the safe boot test are as follows:
Search was snappy, but only produced results from Dictionary (spotlight limited in safe mode?). The _XPC connection was invalidated_ was present in the console logs.
Console output from guest account usage (searching for "Spotlight" in results):
10/8/15 4:11:05.407 PM Spotlight[39213]: spot: agent checkin
10/8/15 4:11:05.496 PM SpotlightNetHelper[39253]: ### Failed to load Addressbook class CNContactNameFormatter
10/8/15 4:11:28.006 PM SpotlightNetHelper[39253]: Connection error while checking Apple Internalness. Error: Error Domain=NSCocoaErrorDomain Code=4099 "The connection to service named com.apple.CrashReporterSupportHelper was invalidated." UserInfo={NSDebugDescription=The connection to service named com.apple.CrashReporterSupportHelper was invalidated.}
10/8/15 4:11:51.904 PM SpotlightNetHelper[39253]: CFPasteboardRef CFPasteboardCreate(CFAllocatorRef, CFStringRef) : failed to create global data
10/8/15 4:11:51.906 PM SpotlightNetHelper[39253]: CFPasteboardRef CFPasteboardCreate(CFAllocatorRef, CFStringRef) : failed to create global data
10/8/15 4:11:51.906 PM SpotlightNetHelper[39253]: CFPasteboardRef CFPasteboardCreate(CFAllocatorRef, CFStringRef) : failed to create global data
10/8/15 4:11:51.907 PM SpotlightNetHelper[39253]: CFPasteboardRef CFPasteboardCreate(CFAllocatorRef, CFStringRef) : failed to create global data
10/8/15 4:11:52.313 PM Spotlight[39213]: applications query - started
10/8/15 4:11:58.355 PM Spotlight[39213]: applications query - finished in 6 seconds
10/8/15 4:12:56.660 PM Spotlight[39213]: Connection error while checking Apple Internalness. Error: Error Domain=NSCocoaErrorDomain Code=4097 "connection to service named com.apple.CrashReporterSupportHelper" UserInfo={NSDebugDescription=connection to service named com.apple.CrashReporterSupportHelper}
10/8/15 4:18:18.547 PM Spotlight[39213]: [QL] After retry, preview was from a different type for <QLPreview 0x7f90152f9820 128039 file:///Users/bubba/Documents/Not%20a%20nother%20way.pages>
10/8/15 4:18:47.761 PM SpotlightNetHelper[39253]: [SLSUGGESTIONS] Location managed failed with error Error Domain=kCLErrorDomain Code=0 "(null)"
10/8/15 4:19:05.155 PM Spotlight[39213]: [QL] After retry, preview was from a different type for <QLPreview 0x7f90154cae00 93211 file:///Volumes/New%20Butter/not%20transient/Law%20Schools/law%20school%205/moo t%20court/OFF%20-%20BRIEF.doc>