It's been working very well for me, I completely replaced Dropbox, and on the VPS/phones [0] as well.
The only slow bit I know of is when it's initially syncing too many files (e.g. tens of thousands). Even if they are tiny, it takes a while. I suspect it has something to do with the index serialization, but also there is a maxConcurrentWrites setting which is 2 by default -- perhaps on an SSD this is an unreasonably low default? Not sure.
Is it possible that you didn't have inotify enabled (fsWatcherEnabled)? There is also fsWatcherDelayS [0] setting (10 by default), which groups changes to avoid excessive sync operations, so it might be percieved as latency.
Three laptops on the same wifi router all talking to each other at once can be very problematic, especially if it's an inexpensive consumer router with one radio. Only one device can shout into the wifi ether at once and the protocol has backoffs to make sure multiple devices don't clobber each other by talking at the same time. Add on top of that other backoff strategies in higher level protocols like in TCP and you can have abysmally slow connections for anything.
I set up Syncthing for my dad a few weeks ago, between his PC and his laptop. At first the sync was incredibly slow, and it turned out Windows on both machines though the local network was a public one, so they weren't talking directly to each other but through a relay out on the internet. I fixed that and it got 15-20 times faster. Maybe you have the same problem?
When I was syncing over mobile hotspot (LAN) on 2.4GHz, speeds weren't impressive. But then I got a 5GHz router with 3 devices and there is sufficient bandwidth. I share ~120GB of total data, spread across ~20 directories, largest being WhatsApp media backup with thousands of crappy low-quality photos. If I wait over a week, I easily accumulate more than a GB of data and it syncs in few minutes at most. Absolutely robust, and zero friction.
I was syncing files on 3 laptops on the same WIFI and the speed was just abysmal.
That was about 2 or 3 years ago so maybe it's better now.