Care to point out a few? I'm talking within the same family of panel technology, not between technologies.
Dell 2408WFP and EIZO FlexScan SX2461W: Both 24" PVA panels, worlds of difference in quality and price. I've owned both of these, and I can tell you after returning two of the 2408WFPs these monitors are not even in the same league. Granted, the EIZO is
way more expensive than the Dell. I actually have a refurb, which supposedly was a demo unit. I came up about $1000 short on a new EIZO, but the refurb arrived in mint condition and it is hands down the best 24" LCD I've ever owned.
Planar PX2611W and NEC 2690WUXi: These two screens share the exact same IPS panel, but according to users these LCD's really aren't at all the same. I have no personal experience with either of these, so I only have second had reports to go on.
HP consumer (TN panels) vs. pretty much everyone else's consumer models: HP has switched their entire line of TN panels to a glossy display, while most of the other manufactures have stuck with matte. The glossies tend to have better color depth/contrast at the expense of reflections. It's really a matter of personal preference and the intended environment with regards to which is 'better'.
Wide gamut: Some PVA and IPS LCDs are wide gamut, some are not. Within the subset of wide gamut LCDs there are also different "widths". Dell advertises a
110% color gamut, while HP touts
102% color gamut on their comparable LCD.
1:1 pixel mapping: some LCDs support it, some don't. This may or may not be an issue for you depending on your intended usage. However, I imagine there are a decent amount of people out there running their 360, PS3, or watching HD movies horizontally stretched on their "better than 1080p" 1920x1200 LCD because it doesn't support 1:1 pixel mapping.
If you think LCD's are all the same, you either haven't done much shopping around, or you just aren't very sensitive to the differences. If it's the latter, be happy it will save you a lot of time and money.