The new icon set plus the new widget integration makes GIMP 2.4.6 look much better than it did. I can't speak for other systems, but on Linux with GNOME it does indeed adopt the desktop style.
The first feature I noticed with the brush was that I could easily draw a straight line. The lines at the top were not done with holding down the shift key; instead it seems to detect when you're trying to go straight and keeps it that way.
The brushes are scalable, and in addition to pressure sensitivity, have "jitter" as well, making it so you can drag straight while applying a scattered trail. Altogether, the brush is much better and the functions are combined well in one dialog. The same attributes apply to erasers, pencils, etc.
The selection dialogs are now movable. This is handy when you want to draw a circle and just miss the guide. After laying the selection down, you can move it with the handles in the corners. Unfortunately this only works with the square and circle, but you can still get other shapes by making a path and doing path-to-selection. You can also round the corners; even after you've made the selection. To compact a couple of points, the crop tool works in similar fashion.
The old "align visible layers" entry at the bottom of the layers menu has been reinvented and turned into its own tool in the toolbox. You will be clicking furiously here and doing nothing until you follow the rules: (i) The selection must be floating. (ii) The dialog from the tool must be open. (iii) after you get the tool, you must click inside the selection you want to move. (iv) You cannot use the arrow keys like with the move tool. You have to click the arrow icons in the dialog.
This brand new tool could use a tutorial or two all by itself. But you first use the tool like the lasso, drawing around the object. Then it will turn everything not in the selection blue. Then you use paintbrushes to draw in the foreground, and cut away background. Each time you do so, the program will update the selection.
Something I've learned is that you do not click on another tool while using the foreground selector or you will lose your selection. Also, you may think you have the whole foreground painted in, until you hit enter and discover little holes in the selection.
That being said, it isn't all that different from the usual masking techniques out there; it just combines several steps and tools into one tool. I'd still want to use colour channels and intelligent scissors along with this selector, either before or after. Still I am delighted about this feature. Masking is a huge pain, and any new tools I can use to tackle it are a winner in my book.
The dropper tool in the color dialog can now pick any color from your desktop, not just from a GIMP window.
The text dialog has a new function. To do this, you have to draw a path first, then put in text, then click text along path. This gave me an outline path which I then had to fill with the paint bucket. But once again, as always with curved text, this is a job for vector editing and not raster editing. It is good but I'd still rather do delicate text manipulation in Inkscape and then export it as a PNG.
As you can see, there are lots more new features all over the place. It really does show that they went back to the drawing board with the new GIMP. The new features are a fantastic improvement, and I will be getting some use out of most of them.
The GIMP development team is very small, as are their resources. Making GIMP more powerful is a worthy use of those resources. Dumbing GIMP down to make it more Photoshoppy just because someone moaned that it's too hard to learn is a huge waste of talent, time, and resources.
If GIMP had the money and patents of Adobe, and Adobe nothing but a GPL and the tiny band of developers GIMP has, GIMP would be held up as a shining achievement that Photoshop could not match.