I should clarify some of the points Prodo makes.
Gamut has more to do with backlight technology than the panel type. There are a few types of available backlights: standard gamut CCFL, wide gamut CCFL, W-LED, and RGB-LED.
standard gamut CCFL is the oldest variety, but still seen pretty commonly. It is being phased out for W-LED though. Standard gamut means 98-100% sRGB gamut, or about 75% AdobeRGB coverage.
W-LED (white LED) is what you get when they talk about LED backlit monitors. It also has sRGB gamut, and is found in virtually all "LED backlit" monitors (including all monitors made by Apple).
Wide gamut CCFL is what you get when you see a monitor with wide gamut advertised (98-110% AdobeRGB). It is the most common backlight when talking about wide-gamut monitors. It's more commonly found in the larger, higher end monitors that are wide gamut.
RGB LED is relatively rare and only a few monitors had this. However, it is capable of producing the widest gamut (up to 120-130% AdobeRGB?), and also the most accurate color (because you can finely tune the color of the backlight). This is only found on very high end, very expensive monitors. In fact I only know of one RGB-LED monitor still made; it's a $2000 model sold by HP.
Where backlights give you the gamut, the panel type gives you the viewing angle.
TN panels are the most common and cheapest kind. With the worst viewing angles. Frankly at this point in the game, I would not bother anymore with TN monitors unless you were forced to (such as with a laptop, where virtually all laptop screens use TN). TN still has use if you want a very high refresh rate monitor such as one that can display 3D images. TN is the only panel that can do 120Hz, but I believe 120Hz IPS monitors are coming soon too.
PVA/MVA is sort of an "in-between" panel type that has better viewing angles than TN, but not quite as good as IPS. VA panels are known for having very good black levels/contrast though. While VA is still seen in LCD TVs, as far as computer monitors go, they have become harder to find, since the generally superior IPS monitors have come down in price.
Then there is IPS. While there are some very subtle differences between IPS types (S-IPS, H-IPS, e-IPS, etc) but they all have a very wide viewing angle, very stable and the picture will not change based on your head position.
For photography, getting an IPS monitor (or VA but they are not as common nowadays) is IMHO very important. Especially since the cost of IPS monitors has come way down in the past couple years, there really is no reason not to get an IPS monitor, period. I bought a 23" IPS monitor a few months ago from Dell for like $250. That's a bargain. Although you can calibrate a TN monitor to produce pretty accurate colors, you will experience color shifts based on the position of your head, and that can lead to variation and errors. Especially if you have a larger monitor, where you will see a difference between the top and the bottom of your screen, even without moving your head, because the difference in angle from the top of the monitor to the bottom is large enough to see visible shifts. This color stability with respect to viewing angle is what makes IPS so good for color work.
As I said before, backlight and panel technology define gamut and viewing angles, respectively, and there is no correlation between the two other than cost. So while it is possible to have a TN panel with wide gamut- it's just that a wide gamut backlight costs more and matching it to a cheap TN panel doesn't make sense as far as product design, so you do not see them in the marketplace. That is why you pretty much only see wide gamut monitors being IPS, leading some to mistakenly conclude that IPS monitors are all wide gamut. However in reality they are separate things.
Most entry-level IPS monitors only have standard gamut, and honestly that's pretty fine for photography, since most people viewing your work will only have standard gamut screens too, or most commercial print houses use sRGB-based print processes.
If you are more serious about photography, have a higher budget, and also do a lot of your own printing, stepping up to a wide gamut monitor may be worth it. 24" wide gamut monitors can go for around $400-500, so even then it is not a huge cost to get a wide gamut monitor.
Personally I use IPS LCDs that I bought a couple of years ago and they are standard gamut CCFL. I bought another IPS monitor with W-LED recently but use it on a different computer. I've been very happy with my monitors and not had any real problems using them for photography. When I get new screens though, I will go for larger screens and also wide gamut.
Ruahrc
P.S. all of the above is totally independent of the topic of monitor calibration. While an IPS screen may have the ability to provide more accurate colors, there is no guarantee that it will actually do so "out of the box" unless it is calibrated. For that you will need to borrow/rent/buy a colorimeter or spectrophotometer to calibrate your screen. Calibration will greatly benefit every screen you calibrate- whether or not it is TN, IPS, standard gamut, wide gamut, etc. If you are at all serious about photo editing or printing, getting a calibrator is a must.
