The different panel types really are a big deal, particularly for us photographers.
Cheaper panel technologies can have very poor colour reproduction and or colour shifting (where the colours change as you look from an angle). The vast, vast majority of LCDs purchased today have bottom end panels; most are TN. If you want good colour accuracy, steer clear of these panels. Unfortunately, this means spending close to double as much.. but the difference really is night and day.
Look for IPS and VA (incl. MVA, PVA) panels. The high quality panels are mainly VA, and the premium quality panels are often IPS I think.
I have a Dell 2408WFP and am extremely happy with it. It has an S-PVA panel, giving excellent colour accuracy (and true 8 bit colour).
Unfortunately, this panel has a terrible input lag (
not response time; input lag is lag caused by the image processor, and not the panel cells) of ~60ms, making it a poor choice for gaming (alternative brand offerings are half that, at ~30ms). Apart from that, it's a gem.
tftcentral.co.uk FAQ - good FAQ
LCD24-7.info - great site for looking up specs of 24 inch monitors