I would not say dislike so much as annoyed, in no particular order -
Stacks - good idea in principle but poorly implemented, the problem is really compounded by the removal of hierarchical folders in the dock.
The translucent menu bar, it not only looks bad but the fact that it is dim gives the impression that it is somehow 'inactive', when the app it is for is active.
Setting Finder views has changed, views now have to be set individually for each folder otherwise the last view you set follows you around like a bad smell. It is possible to get used to this and set views as you go but when using the back/forward buttons the view you set is ignored and the last one used comes back, or in some cases a completely arbitrary one.
Inactive windows now turn nearly white, get a few of them together and they just merge, making it difficult to tell them apart.
Folder actions keep getting disabled arbitrarily, I set them and a little while later they are gone for no reason.
I have the dock on the side so the 3d dock is not an issue for me but even on the side the dock now has a dark background with a white border, take this and the translucent menu bar plus the new window style and there are three different elements on screen that are all jarring to look at.
These are just my gripes BTW, lots of people seem quite happy with Leopard and under the hood it is still as stable as ever, as I mentioned some of the new features are actually quite good like quicklook and the rewritten spotlight.
Also, I know stuff like the menu bar can be changed now but I found myself changing it so much to work like Tiger I thought I might as well go back
