I’ve been running 1.6 since the day that it was released. I have 1000+ albums stored on my server and have had an additional 3000+ titles ‘saved’ to my library each from Qobuz & Tidal subscriptions (although I recently have removed the Tidal database). My initial experience was similar to what I see reported in this thread. Very slow and unresponsive (relative to what it had been in 1.5), particularly in searches.
That has gradually changed and improved over time and with continued use (and I use Roon daily). As I write, 1.6 is now just as fast and responsive as it had ever been with 1.5. I no longer experience any slowdowns and never wait longer than 1-2 seconds (sometimes less than that) for any function or click, including ‘Search’ function.
I’m relatively certain that (in other threads) Roon staff have stated that the responsiveness will increase over time and use and that has born out for me. If memory serves, a period of time as much as a week or two was even suggested. Just keep using and (hopefully) your experience will be the same as my own.