I have to say that the UI of 5.0 is really bad.
It looks like a child sat down and tried to copy what he/she saw, by memory.
It has been my experience that creators/companies that decide to "improve" the UI of their products rarely care about the opinions of their user community.
Complaining about it will probably not move them to reconsider the changes. In their minds the "more modern" design will always look better, just because they designed it.
Anyway, if the updated UI goes ahead, I'll likely stay with version 4 until I can find a replacement program.
I am a diehard Windows XP user, and the new UI looks so out of place that it would be difficult to continue to use it.
My plans are to build a nice Windows 7 machine, but it probably looks just as bad there.
Obviously, designed with Windows 8 in mind, and with little consideration for everyone else.
It's going to be a sad day indeed, when version 5 makes it's debut.