I've been following along the fiasco that is Psystar and noticed that a recurring theme in many forums was the comparison of the machine proposed by Psystar to the Mac Mini.
At the risk of being horribly cliché, this is comparing apples to oranges.
The Mini is the machine that begs the comparison since it's the closest thing that Apple sells that targets the entry-level market. But there are a number of very important reasons that this is pointless, leaving aside the entire OS X compatibility question (more on that later).
You simply can't compare the price/performance profiles of these two machines without also factoring in the impact of the form factor. The Mini is very very small and the PC equivalent is based on a nano-ITX motherboard. In a tower case, you have many more options for the motherboard and physically more space to put things, which means more connectivity options and better cooling which means more powerful components. You're buying a motherboard that is very mainstream and produced in relatively high quantities for multiple PC-builders.
Obviously when you make something that small you are limited in your choice of components. The Mini uses a 5400RPM 2.5" laptop drive, whereas a tower design has the space to physically hold a larger 7200RPM 3.5" drive and the ability to cool it. Right away this gives the performance advantage to a larger machine, but it comes at the cost of size. Now depending on your needs, this will be more or less important (witness how many people use a notebook computer as their primary machine). A laptop drive can produce perfectly acceptable performance, up to and including running virtual machines, photoshop and even small scale video work.
Would it be faster with a faster drive? Of course! But there's no room in a Mini for this kind of drive. You can gain the benefits of a faster drive by either adding an external drive connected by Firewire or if you're feeling ambitious and really want the speed boost, you put a cable on the internal SATA connection and pass this out to an external SATA drive. Obviously the SATA connection outperforms the Firewire connection, but comes at the price of having to do some pretty serious modifications.
Not much to say here as it's hard to buy a computer without an ethernet card (probably gigabit) and possibly an integrated Wifi card of varying modernity. The only hiccup here is price. Laptop components are going to be more expensive that desktop ones.
We're again dealing with the issue of space limitations. If you have a tower with PCI slots, you can select the video card you want, but in a Mini, the choice is pretty much limited to on-board graphics. That said, the Mini's video is a pretty competent as long you're not playing 3D games. I have a Mini setup connected to an LCD TV at 720p and it's quite capable of handling this style of HD content. It does strain when downscaling 1080p content to the 720p resolution. I don't have a 1080p screen to test against to see if it would be less stressed if the content matched the resolution.
This is a huge deal and something that is overlooked in the standard specifications list. I think that every computer should come with a dB rating at idle and under load. I had originally bought a Shuttle to use as a media station in the living room as it was reasonably compact, decent hardware. That lasted all of a week after it got packed off to the office due to the noise issues. Office environments are more forgiving for background noise, but quiet environments like a living room (assuming no kids...) you can pick out each individual contributor to background noise and they're noticeable.
At the risk of grossly oversimplifying the situation, the claims made by Psystar could also be made by just about any PC manufacturer out there right now. If you have the time and the technical chops to do so, you can run OS X on most modern Intel based hardware as demonstrated by a number of recent articles in MacWorld. You need to find a way to boot OS X off a BIOS based Intel machine and have the appropriate drivers for the hardware. Nothing terribly complicated here, just a PITA since these pieces aren't built into the installer. Note: You can run the Darwin layer legally, although that's not the part of OS X that most people are interested in.
If you have the time to burn and like playing with this kind of thing, have fun! I know that when I was younger and had more spare time on my hands, this kind of playing around was immensely satisfying and taught me a lot about how computers work. But if you depend on your computer as a business tool, then I would say that this is not really a good approach to saving money since you'll invest a fair bit of time getting things running (although the pre-installation service from Psystar will help a lot) and you can't simply run Software Update and be sure that you'll have a running machine afterwards unless you do your research for each and every update that comes down the pipe.
I'm hoping that all of the noise and interest will communicate to Apple the market demand for a modular machine between the Mini and the Mac Pro. It's clearly the gaping hole in Apple's current line-up as a computer vendor. But looking at it from Apple's perspective as an innovator, what can they do to stand out from the crowd in this space? The iMac's all-in-one design is now being copied, but they were the first to really get it right and make an impact with this style of machine. The Mini is still the best price/performance option in it's market niche. The new MacBook Air is a whole new class of laptop.
Apple's not going to sell anything that they can't trumpet as being the best of class in some way (at least at launch). The Mini was the smallest full featured computer, the iMac the simplest, the Air the lightest, the Pro was the fastest.
What superlative can you attach to a mid-range tower? Hint: Cheapest is not an option.