I have used HiveAlive for several years - in both spring and autumn feeds. Bees do build up well in the spring. The effect on nosema is such that we have not seen it in any of the 14 hives. The thymol content prevents the syrup from going mouldy. I would also add that since using it varroa levels have been low - this may be a coincidence as there is currently no suggestion that HiveAlive has any effect on varroa. We would not feed syrup without it.
"Norton
,
"Thymol in syrup renders male mites sterile, does the same to drones!"
From the thymolated syrup thread,
http://www.beekeepingforum.co.uk/showthread.php?t=26305
He wouldn't substantiate when asked though, but it's definitely a suggestion.