I like my sergers and use them frequently.
The initial threading or if one has to rethread it for some reason is a pain - I've learned to poke a stiff thread from the 'top' through a couple of the parts/guides and then tie the serging thread to it and pull it through. Just couldn't get that thread to go through those guides by itself.
I've bought any number of things that it turns out I could have gotten along nicely without.
I am also surprised at how many people have been less than thrilled with the die cutters and the John Flynn frame.