Thanks for your message, you explained everything very well.I switched over two years ago and I had the exact same sentiment as the OP regarding my mac experience. The mouse acceleration was not what I was used to, somewhat delayed and the GUI(Graphical User Interface) of the OS is not as instant as Windows.
I agree to this day that what the OP is describing is very real. I work all day on Windows machines at work and I use my mac at home.
But I have learned to accept it. Otherwise I would be missing out on too many good things the mac experience has to offer.
First of all, I will address the mouse acceleration curve. Yes it's not windows smooth and its not as responsive. The Delay is there. There is no denying it and there are many reasons why its like this and I will only touch on a couple.
The acceleration curve has graphic artists in mind. Apple made a compromise by allowing the mouse to travel at low speed for a bit longer then in Windows to accommodate any kind of jerkiness or mistaken movement of one's mouse while doing precise work in a very small area of the screen. I am not a graphic artist and I wish I could turn this off. I would pay good money to have a mouse cursor in OS X that felt like Windows or most Linux distributions.
Also, Mac OS X has a mouse cursor that I believe is somewhat aware of the objects around it. I like to call it a magnetic cursor. I have never seen any official statement from Apple (or anyone for that matter) that such a feature exists in OS X but I am quite confident it exists. Buttons, sliders, URL links and menus will actually pull your mouse cursor towards them. This is extremely subtle and is almost unnoticeable by the user unless you move your mouse very slowly around such objects. Then you will see it jump slightly towards the object by a couple of pixels. This feature often gives the mouse cursor a jumpy and/or jerky feel at very low speed.
Now let's move on to the "heavy" feel of the GUI. This is due to to two main things in the design of OS X:
The first being that OS X will not draw a window for you on screen until it is completely drawn in memory. In windows, you often open a window or menu and you see things get drawn onto the screen one at a time in front of you. That's because they have not been drawn in memory yet and Windows is just giving what it has when you ask for it. OS X is different in the sense that it won't give you what you asked for until it is completely ready and drawn in memory. So there is always that fraction of a second delay while OS X handles this. This is the same idea as the "Vertical Sync" graphical setting often used in video games.
The Second reason, which you may not understand (and I don't blame you), is that OS X is heavily object oriented due to the underlying NextStep design. I will not go into details because I could spend all day trying to explain this to non-programmers. But essentially, this makes every component on screen larger in memory and one component may need to talk to several other components before being able to talk to the one it wants.
This second reason was much more noticeable on the PPC machines and the very first intel machines but with the memory speeds that are out now, it should be a non-issue.
What I did about it:
I found that high precision Mice, like my Logitech G5, would accentuate the differences of the mouse movement in OS X relative to Windows. I ended up finding the Mighty Mouse to be the mouse that made the cursor behavior the most bearable.
I also agree that the mouse movement on the trackpads is heavenly. This got me thinking and when I move the cursor with the mouse, and imagine that the mouse is on a large trackpad, i realize that there is no difference. I don't know but often things are all about perception I guess.
As for the heavy GUI, I just accepted it. If something is not up on the screen its because its not ready and if it was on the screen before its ready, i'd be waiting for things to get ready anyways.
Sorry for the wall of text but I hope this helps you in making an informed decision.
Good luck!
The guy from TNT came this morning at my place and took my iMac.
I called Apple on Friday and now the iMac is already gone. I have never seen a customer care as good as Apple's.
Now, I think I'll buy the Dell Studio XPS Desktop. Here is what I would get for the same price:
Pentium Core 2 Duo 2,93 GHz
Windows Vista 64 bits
Microsoft Office 2007 Family and Student
24'' screen
1.5 TB Hard Disk Drive
12GB of RAM!
ATI Radeon 4870
Blu-ray writer/reader + CD/DVD
It looks like this (but the screen will be far bigger):

So, a Blu-ray reader + writer, 500GB more of HDD, 4GB of more RAM... all of that for the same price.
Yes, the design is not as good. Some will say that there is iLife on a Mac, but I use professional software for this.
Anyway, I will take a smaller configuration and save money. I just wanted to compare.