I really hate to say it, since I really like Logos 5 as far as all the other aspects, but it is about 25% slower than Logos 4 was for me. I never had a big problem with Logos 4 from the beginning, though I know a lot of people complained about the speed. At the end, Logos 4 was positively snappy on my system. It seems that they changed something that made everybody else's faster and mine slower. Strange. What makes other's faster makes mine slower.
Another thing is it keeps crashing when I try to rearrange the prioritization list in my library. It crashes almost every time now.