For over a year I've been happily working in ArchiCAD20, without any noticeable delays in 2D or 3D.
Recently I've started having problems with the 3D preview 'thumbnails' (objects, windows, doors, favourites) where they generate really slow (like a few seconds). This is mostly annoying when picking a favourite from a long list waiting for the thumbs to generate.
I've been in touch with reseller and sent some diagnostic files to Graphisoft, they are looking into it.
But until recently, I would have said ArchiCAD20 is very solid on windows 10 and my workstation is a good 5+ years old at this point.
The update cycle from 18 to 19 to 20 has been painless too, so I have no old projects that I am currently running on anything else than 20.
Still haven't dived into 21 yet.
Looking back: ArchiCAD15 was damn solid, but 16 too after it received some updates and 16 gives you morphs, which in terms of modelling tools brings you close to what we have today.
17 gave me no issues either, which would mean that at least they're working with building materials.
18 means you have cinerender and also is very easy to upgrade to 20, if you would want to.
Going to 21 means dealing with no stairmaker, so personally I would not migrate a running project, since 20 is pretty solid (at least until recently for me).
Erwin Edel, Project Lead, Leloup Architecten
www.leloup.nlArchiCAD 9-26NED FULL
Windows 10 Pro
Adobe Design Premium CS5