What should I do if my computer exhibits one of these problems?
If it is within 14 days of receiving the computer Apple will give you the option of receiving a brand new one. Although this means sending back the faulty iMac and waiting up to 3 weeks for a new one to be shipped to you. You also have the option of having it repaired. If any problems show up within the first year the standard Apple warranty will either repair or replace your computer (although the replacement could be a refurbished model). If you opted for AppleCare then in certain areas Apple will send a technician to your location to fix the problem and you will be covered for 3 years.
Should I purchase AppleCare?
You should purchase AppleCare if you want some extra piece of mind but I've always found that if there is a problem it will show up in the first few months. As for the new iMacs no one really knows how solid they will be in a couple years time but if there are any issues Apple will rectify them (they have often extended warranty coverage of previous models that were found to have defects).
Should I purchase a new iMac now or wait until all the manufacturing problems are fixed by Apple?
Apple has historically been very good about extending their warranties to cover any defects and they have great customer service so the main question is whether any possible hassle of dealing with a return or repair is worth the risk to you. Some of the problems such as the cracked glass appear to have been resolved with the more recent builds. Only Apple knows the true defect rate with these computers and the data on this web site is a bit skewed towards faulty iMacs as people with "perfect" computers wouldn't have a reason to visit here. There are bound to be some issues with any manufactured product and Apple ranks pretty well compared to other manufacturers (the average rate of failure is around 17%). So, I think you can buy with confidence either right now or in several months after Apple solves their manufacturing problems.
How accurate is the data on this web site?
The data presented here is based on information submitted by people on this web site or taken from comments posted in Apple's Discussion boards (this is an "unscientific" survey and as such should not be considered representative of all iMacs sold). However, all submissions are checked over and any duplicate or "suspect" entries are corrected.
Has Apple fixed the manufacturing problems yet?
As of January 16 people are still receiving faulty computers that were built early in January.
Is the frequency of problems decreasing?
If you look at the week built data (far right column) it looks like that more recently built computers have fewer problems (which is deceiving). This graph shows the number of submissions per week and as people are only starting to receive computers made in the last 2 weeks that is why the numbers look a bit lower. As people start to receive more recently built iMacs these numbers will start to increase.
Things do look a bit better regarding issues with the newer batches but many of the same problems are still occurring. When you look at the current data for some of the more recent weeks the number of "perfect" machines is remaining around 30%: Week 53 2009, Week 1 2010, Perfect iMac data. The best way to see if the problems are in fact decreasing over time is to look at the relative build quality for each week of production.
Another reason for the apparent decrease in numbers is that the media aren't covering the issue as much right now (although the number of visitors to the web site is remaining pretty consistent). This story never hit the mainstream media either so only people who visit Apple's Forums, MacRumors, tech blogs, or find it using Google know about the problems. However, new reports are continually being added (several hundred per week). I would also have to guess that fewer people are buying iMacs as well (the biggest backlog would have happened when they were first introduced in October). And if Apple in fact did slow down production (as was rumored) then that may account for the big dropoff after Week 50 as well (they are still listing 2 weeks production time).
Are there more problems with the i7 or 27" models?
No, in terms of problems all the models are pretty comparable: 3.06 Core 2 Duo vs. 2.66 Quad i5 vs. 2.8 Quad i7. All the distributions (graphs) look pretty much the same. And none of the things like flickering display or yellowish screen are really a result of the processor. It just happens that more people are buying the i7 model so there are more out there (and more people are buying the 27" screens as well). The number of "perfect" i7's outnumber the other models as well. One thing that this data does show is that the i7 is really popular.
Is the screen flickering a hardware or software problem?
Apple did release a firmware update which may have fixed the problem for some people but for others the flickering is still happening. Most of the successful repairs have involved replacing the LCD screen, LCD cable, and/or the GPU.