If you have an iOS device, the third party app SmartRules (a nice rules engine app that costs about $10) has a $2 add on that can detect IBeacons and use them as a device with SmartThings. Quite a few community members use it and like it. I found it well worth the money. 
( They are working on an android version, but don’t have one yet. )
Or if you use an iBeacon app which can do an http:// POST, you can use the IFTTT maker channel to connect to SmartThings. I use IBeacons quite a bit, and I also like the beacon sandwich app because it has a nice Apple Watch option ( it can’t track your location by the watch, but you can use voice commands with it and get notifications). So that’s another easy way to include I beacons with SmartThings.
You are of course right that there can be some delay. So they work better for some use cases than for others. I like them because I can set them to a very narrow detection range which meets some of my needs very well.
I think microlocation presence is one of those things where different people can have very different requirements depending on the exact set up of their house. The number of different people come in and out, whether those people typically always carry their phones with them, the specific architecture, the budget, etc. are all factors that vary a lot.