Perhaps it's because there are so many similar threads on this topic right now, but I tend to agree with GGJStudios on this one.
At a certain point, your own usage and preferences will trump anything else anyone has to say. You can't constantly worry that you haven't thought of something to ask. Maybe you haven't thought about Issue X because Issue X has no bearing on your own computer life. I've heard people saying that they've gotten a bigger screen Macbook Pro because they do a lot of Photoshop work. That's a completely valid reason to go for a larger screen. But because I personally do little-to-no Photoshop work, so even though it's a valid concern and someone may have regrets about not getting a larger screen, it is irrelevant to me.
I just think putting out a broad question like "do you have regrets?" doesn't really get you anywhere. You've got to narrow it down at least little bit. At least say "I'm thinking of getting X computer to do A, B, and C. Does anyone who also bought X computer have regrets?"
For what it's worth, I have regrets that I got a 13-inch Macbook. I sometimes wish I gotten an iMac, because I notice that I have a tendency to sit on the sofa and surf all day on my Macbook instead of reading books or exercising or doing other important things. This is a real regret for me and it may mean that my next computer will be a desktop. I'm less inclined to sit all day in front of a desktop computer. And I wonder if the portability is worth the time that I've wasted screwing around on message boards

The Macbook is a great computer, the problem is me and my usage, not the computer itself.
Now, does that *really* have any relevance at all for the OP? I would suspect not. And that's okay, because I'm not him, he's not me, etc.