* the bezels don't look native (but look pretty much like 1990 toolkits like Motif)

* In your first screenshot:

- The checkbox seemingly changes size whenever it's checked or not.

- Likewise for the radio button, and the "small" one for some reason seems aliased or something like this.

- The small Tk logo in the tree view is also aliased and let's not talk about the canvas which looks like it's taken straight from a 1990's example.

- The tab sizes are weird and the spacing between the icon, the text and the border is uncanny, to say the least. Here's some example with Qt : https://i.stack.imgur.com/eoHaS.png or GTK: https://lists.gnu.org/archive/html/emacs-devel/2010-04/pngNP...

- The form containers (Label 1, Label 2, Label 3, Label 4) all have different sizes ; their bottom should be aligned.

* For your second screenshot, hre's another one fairly similar in concept (looks like it's made with GTK), but much prettier:

https://i.stack.imgur.com/7v6Ja.png

The most blatant thing is that the label "Direction" isn't aligned at all with the widgets that follow it. The placement of the widgets seems quite random, too. And why is there so much vertical spacing between the three rows of widgets ? But overall, notice how all the widgets in the GTK one line up nicely and have consistent margin and padding.

As an example I did a rough sketch (without caring too much) of the UI of the first screen shot with Qt. It took me 17 minutes (http://sendvid.com/f6gbp6el), with no prior try and without of a lot of habit with the Qt designer: https://i.imgur.com/4MLh48R.png and already I find it to look more professionnal (except of course the goofy canvas try :p). Another fifteen minutes and I feel like most of the Tk ui could be matched without too much stress.