The problem is that data still pass through the PCI bus. Even if you get an add-on card this limitation still exists, it also exists on the gigabyte mobo you linked at (no SATA 3 or USB 3 with 2nd PCI slot occupied). What's the point of upgrading if the speed gain is minor or gets in the way?
Anyway, asus seems to have a more "proper" implementation on some of their mobos.
Edit:
New technologies is a reason to wait in my opinion. Like the AGP to PCIe change, or the IDE to SATA, or even the different CPU sockets. You don't get a new PC to be unable to do any sort of serious upgrade in the long run. Imagine being limited to USB 1 and IDE speeds for your current system. Imagine trying to find a first party AGP video card with acceptable performance (only radeon AGP cards perform relatively well but AMD does not even support them).
Well, you're right about the first part. That obvious bit about it completely passed by me.
I still think delaying an entire build over USB 3.0 or SATA 3 is not worth it. Your examples of a CPU or GPU don't help. They're major parts. I even said myself that I'd wait for those, but even then, only if they're right around the corner. USB 3.0 and SATA 3, on the other hand, are not major parts. These are minor technologies, and it's not worth delaying an entire build for months over them.
They will make
no difference to him during that PC's time on the top, nor during it's mid-prime, nor probably during it's later years (it might by then, but by then, the stuff would have to be radically ahead enough to where the whole thing would need replaced anyway). Hard drives needing 600MB/s won't be here in the next two or three years, and what will really need USB 3.0 besides external drives that your typical enthusiast will use? Nothing. He gains nothing by waiting for these two pieces of technology, and as I said, he does not want to spend alot of money. This won't be cheap at first, which means, you guessed it, more waiting.
You're telling him to wait at least half a year for stuff that means nothing. I don't care if it "eventually" will. I saw the same game with the quad core hype, and I am honestly still laughing at the people that traded in speed for that time period for "future proofing for the future" (I'm talking of those who got Q6600s years ago, not those getting i7/i5s now), when in reality, the extra cores did them no good for what really mattered, and they still aren't fully here yet, and guess what, no, sorry, but they won't be tomorrow either, as much as everyone likes to try and exaggerate the uses of four cores or five hundred threads. By time they (the Q6600s, Q8x00s, etc., the older quad core CPUs) are actually "needed", their time will be past, so, they spent more money for less speed for future proofing that never helped them. Good deal! The best I've heard them come up with in response is "oh well, I don't need the extra speed anyway", but then it begs to question why they even got a quad core CPU with the mentality of "future proofing" in the first place.
There's no such thing as future proofing with PCs. You actually tend to waste money doing that. There exists a thing called smart buying, but smart buying does not equal waiting and/or getting the latest upon release. They're two different things. If there's anything I've learned through my time with PCs, it's that the waiting game is doing you no good. The fact remains that your PC will become outdated just about as fast, and you'll have waited between the time you first wanted it until the time you got it. Like I already said in a previous post, unless it's a major technology, or a major price drop, and you plan on getting it
and it is coming up real soon (within the next month, two at the most), then there is no reason worthwhile to wait. Either go big now if it's longer off, or get a decent and cheap stopgap product, and then upgrade, but even that can bite you (it did with me).
I'm not trying to demean USB 3.0 or SATA 3, as useless for now for most people as I will truthfully call them. I like any new advancement, but I am not going to advise someone else to needlessly wait for months or whatever for what will be 99% useless to them, and perhaps above what they are willing to afford in the end anyway, just because people think they need it to be ahead because it's "going to be standard at some point in the future anyway, so it's the thing to make sure you have now". There is, and always will be, stuff over the horizon. Just get what you want, when you want, and be done with it, and enjoy it.