Let’s start with the technical aspect of Thunderbolt – what it is and most of all: what it isn’t.
Thunderbolt as people probably know is part Displayport. It has a Displayport signal as part of the base of Thunderbolt, which means you can send audio and video to one or two devices (if one device support sending the Displayport signal from it to another device, which almost no monitors right now do!). The other base part if PCI-Express.
PCI-Express is one of the base layers of computers. Looking at a desktop, it’s the thing you use to add any expansion cards to a computer. In current computers (at least for Intel) PCI-E is a near-direct path from the expansion card to the processor, to such an extent that what processor you have decides how many PCI-E ‘lanes’ (like lanes on a road) you have. This is no longer dependent on motherboards.
PCI-E can be used for almost anything. There are PCI-E cards for USB (3.0), for Firewire, for Ethernet, for graphics cards (most famously), for audio cards, capture cards, and many many other things. It’s the most-used way to expand a computer’s functions on a low level.
To make a quick comparison to USB: USB doesn’t have direct access to the CPU. USB exists on a much higher level (this is a bad thing for expansion devices, usually) than PCI-E, which also means it has less access to lower-level functions and parts. USB has to talk to Windows or OS X to even get anything done. You can make mostly everything you can with PCI-E with USB these days, but you’ll get slower, more processor and memory dependent results. There’s not a single graphics card for USB that’s intended for gaming, mostly due to USB’s extremely high latency compared to PCI-E.
Back to Thunderbolt. Thunderbolt feels a lot like USB to most people right now – you hook up your Firewire-converter to it, or an Ethernet connector. Maybe like me you have a nice external hard drive hooked up to it. Those things feel a lot like USB, and since Thunderbolt is so much more expensive, it feels useless.
Well, here’s some examples of why it isn’t.
This is the Sonnet Echo Express III. What it does is allow you to hook up to your Macbook three (!) PCI-Express cards. These can be audio interfacing cards, they can be capture cards or specialized editing cards. You can even put a limited set of full on graphics cards in there, though this one’s not ideal for it yet. With USB, you’d have high latency and CPU usage, and you’re sharing all your USB bandwidth between those devices, but with PCI-E, you get much more and much more stable bandwidth.
I also own a Thunderbolt Display, and that has multiple different PCI-E devices built into it. A USB controller, a Firewire controller, an Ethernet controller and all the things like webcam, mic, speakers and so on. The aforementioned external hard drives are attached to the Thunderbolt Display, and then I have a Dell monitor hooked up to the hard drives. I’m powering two displays, my Ethernet, Firewire, most of my USB and two hard drives (or SSD’s, it’s full SATA so you get full speed) to one connector. USB can’t do that, even if it’s soon-to-be the ‘same speed’ as Thunderbolt.
The comparision between Thunderbolt and USB 3.0 isn’t about speed but about what you can do with them, and that’s where the comparison becomes pointless. Thunderbolt wasn’t designed as a replacement for USB, even though it can be if you want it to be, it’s designed to replace desktops. Thunderbolt is designed to make a notebook capable of truly replacing a desktop computer in terms of expandability. Thunderbolt was designed to make on-the-go high-performance audio and video devices possible. It isn’t close to cheap, I agree, and it’s not for everyone, but Thunderbolt is amazing.
The technology behind Thunderbolt sets it completely apart from USB, which was never intended to do as much as it does now, and it’s completely and totally different from it. While Thunderbolt isn’t for everyone and not everyone even has a use for it, it serves its purpose extremely well.