If you think perl/Tk looks awful (you're allowed to think so, I know more people that do, but it still is an opinion), tcl/Tk won't change a thing! It will look just as ugly (or beautiful) as perl/Tk. It is all Tk in the end.
If your perception of nice/beautiful is that it should match the native window styles, and zillion of people will agree with you that that is what they expect, than you should change to Wx. Be prepared to a whole lot of work in rewriting your code. The pro of Wx is that your portable App will look native on all platforms. The con of Wx (compared to Tk) is that you need a lot more code and that the App does not look the same in every environment.
It may be obvious that I prefer Tk, but I also understand that people say it shows its age.