I too find searches and sync's slow. I too compact before each sync and have the top high speed service available here locally (Ontario, Canada).
So i have been watching my timing and find trying to search or sync on weekends after 11 am runs into a clogged Ancestry service ( perhaps the east coast has woken up, had breakfast and are now ready to work?) So, I try to do my work before 11 am and during weekdays.
Might this help? Cheers,