Since we're several of us are here waiting for Apple to sell an iMac with a processor that isn't well over a year old, I began thinking about the age old debate about whether an all-in-one computer is a good thing or a bad thing since you can't upgrade it. This is particularly relevant since a majority of people are buying laptops over desktops these days. In short, it seems to me that the principal reasons to upgrade a computer are for a better CPU, a better display, a better GPU, more memory, better I/O or better peripherals. I would argue that most of these reasons are possible even in Apple's closed AIO offering or probably aren't even practical in a Mac Pro. First, better CPUs over one generation old often require a new motherboard. This isn't always the case of course. If you require a new motherboard, a Mac Pro won't solve your upgrade need. Given that, you might as well be a home builder which begs the question whether Apple should even sell Mac Pros if its clients would prefer to just build the computer themselves. Second, a better display (or larger display) cannot be added to an AIO. This rationale is probably the best argument for an "upgradeable" desktop. That said, one can purchase an external display for an iMac although much of the elegance of the set-up may be lost if you choose to no longer use the original display or purchase a new external display without aesthetic similarities to the original iMac display. This begs the question why Apple's own standalone display isn't more similar in design to the iMac. Third, a better GPU would certainly be nice to add to an AIO. Thunderbolt offers the potential to purchase an external GPU; however, this begs the question why the GPU is being upgraded in the first place? If one needs cutting edge graphics performance, one probably also needs cutting edge performance in the rest of the system which begs the question why wouldn't you just purchase a brand new computer? The question of more memory is similar in my mind to upgraded GPUs. Once you've maxed out the memory and you need faster or additional memory, odds are that the rest of your computer is also lacking other requirements. Better I/O has frustrated me recently. I have a large library of digital video that I want to archive. I waited many generations for a faster alternative to FW800. Thunderbolt seemed to offer a solution, but then we waited for practical offerings at reasonable price points. Meanwhile, USB 3.0 was available with low-cost, high-speed options. I don't won't to debate the merits of USB versus Thunderbolt, but you get my point. Living in the AIO world often requires you to wait patiently for options you prefer. Finally, better peripherals are frustrating for AIO owners; however, external peripherals often can meet their needs. I looked forward to an Apple Blu-ray option again to archive DV regardless whether it came with a "bag of hurt" or not. So, let the discussion begin. Some of my thoughts aren't fully formed yet, but in over ten years of owning iMacs I haven't ever been completely shut down for owning a computer that can't be upgraded. Scientific applications aside, I'm not sure Thunderbolt doesn't offer a way for Apple to kill the Mac Pro. It would be easy to see a Thunderbolt hub that offers all the expansion most folks would ever need.