I can't recall where for the life of me, but I do think I did see some small blurb somewhere on the internet that mentioned that with the introduction of the new LXX30 series tractors, Kubota had a small increase in initial problems with that particular new series over the previous LXX10 series.
I found that when I was having a problem with the new 5030 I bought and was scouring the internet to see if others had similar problems. I did not find anything to alarm me or to even make me think that a lot of other people were experiencing the issue I had. Kubota fixed my tractor (FEL hydro issue) and all is well now. Maybe I'm wrong, but I think just about any tractor maker can have a blip on initial complaints with a new model; I know automakers do.
Based upon my experience with owning two new and one used Kubota is that I'd definitely consider Kubota for my next tractor, but as in the past, will look at and consider other makes as well.