I also would plump down for the iMac. For one, I don't like buying into aging and/or obsoleting technology. If it were $500 to buy some thing from years ago and really wanted or needed it that bad for some specific purpose, maybe. But, to invest 2 grand for resurrecting dying technology? No way! As nigelbb points out though, the new iMac with AppleCare for 3 years protection (want it for that big screen) and worry free computing, a quad core i7, 32GB of RAM, 1TB Fusion (a quasi-SSD) USB3 and thunderbolt for I/O to expand on that 1TB through externals, having both integrated and discrete graphics.... for.... $2600? And, a 10% discount on that making it $2,340? That should be a slam done deal! Personally I am planning to go that route but I am just waiting until the iMac 27" 2012 becomes more readily available and there are some reviews on the product.
Technology has advanced enough that what use to require big beige towers (grey in Apple's case) with noisy and high wattage power supplies is no longer the case. Similar production tasks can be done with the compact, portable and AIO computers these days. Similarly thick, heavy notebooks are giving way to ultrabooks (PC camp), Macbook Airs, Pros. My rMBP alone in and of itself connected to an external 27" can be a workstation in and of itself. I've easily done FCP, Adobe Premiere Elements work with it. Simpler tasks are a given. Talking about the 'heavy weights'. I don't do 3D gaming, or gaming at all for that matter, but, I am quite sure it is capable for that stuff too. I don't like the lockdown on memory and SSD, etc., but, that seems to be the industry trend, PC or Macs, spearheaded by Apple. That is why you pay the AppleCare protection 'tax' on the device. Then, it's Apple's problem for the next 3 years. For myself, prior to that expiration, the machine most likely will be sold on auction. I usually rotate my equipment every 1-2 years to: (1) keep technology current, and (2), to recover a good chunk of my money via auctions. The amount I don't recover is the 'rental fee' over the time of usage with right of ownership should I so desire.
Back to the original point of this article.... building a cheap $900 Hackintosh versus purchasing a MacPro...... along with the price savings (if one can be built that cheaply even) one inherits the headaches, trials, tribulations, and the need for technological know how to make a non-Mac machine work like a Mac computer. Great if you don't mind and are a tinker type. In the final outcome, you hope every thing 'orchestrates' well together. (like plug 'n pray times gone by for Windows). But... if you are into heavy 'RAW' video editting, and really doing it semi-professionally or professionally for a living, making money at video post in RAW (going to create Avatar 2? :-) ) then perhaps you want to go the route of not just one Hackintosh, but perhaps a couple. But, if doing ordinary video editting work, I already do that on my max'd out 2012 macmini for that matter.
One other issue plays on my mind, perhaps maybe not relative to Hackintoshes..... what is the future of MacPro? It takes Apple literally years to come out with a new iteration in that lineup. Why? Well, maybe only one new model once every 4-5 years might be sufficient in spite of technological advancements. BUT....... my contention and gut feeling is, Apple eventually will let that line drop. There's no money in the MacPro lineup, nor volume of sales. They screwed around with Final Cut Pro to the dismay of professionals in the industry when going from FCP7 to FCP-X. The decided to discontinue X-serve. Also, Apple OS-X Server, for the what-its-worth department, used to cost several $100s as a professional server package has come down to being an add on to OS-X that some one can purchase for.... $49 or so? via the Apple Store. Apple's nose follows the money. And, these days, iPhone and iPad is where the money is... not X-serve, not server OS, etc. To a lesser degree, their income is also derived from Mac sales. From a business perspective this is well and good for Apple (iphones and ipad sales). From the consumer perspective though, expecting Apple will continue to feeling empathy for those desiring a new MacPro every year, I don't think it's going to happen. Comparatively, there is no money in it. Similar to the 17" Macbook Pro which is already gone, I believe/feel Apple is going to axe the MacPro line, as they've already done with X-serve. Oh, they may still come out with a new MacPro this year so that Tim Cook remains good on his word from last year. And, I reckon it will satisfy the MacPro campers for the next couple of years. But then, that buys Apple the 'breathing room' to just let that die off if they choose to do so. And, I think they will choose to do so. So, for myself, it is just one more thought / reason I personally will not go with the Mac Pro, not to mention Apple will charge a premium again for a new MacPro model. They are a high priced, high margined product company. For myself, the high end Macbooks, Ultrabooks, AIOs are becoming sufficiently powerful enough. The only thing really keeping me tied to all this 'lock in', 'lock down' so to speak, is the operating system, OS-X. If Apple mucks around with that excessively.... well.... I will cross that bridge when I come to it.
I reckon I got carried away here a bit. Anyway, I hope there is some comment of value to derive as 'food for thought' in the decision process. :-)