It depends on the response rate, obviously a slow response rate isn't going to update the screen very often, and therefore leave a trail behind aka ghosting. But a very fast response rate will update quick enough for no ghosting to be seen.
I don't know what's a good rate etc, but I think that 0.25 or lower will suffice for gaming.. I could be wrong though
some lcd's are pretty bad at ghosting. these are usually the older or cheaper ones. laptop screens in general are pretty bad too.
but i bought my lcd (see sig) on an impulse buy (it was on sale) and haven't regretted it. and i'm an avid gamer. i won't lie and say there's no ghosting, but it's very minor and doesn't detract from the gameplay. i later found out that the dell ultrasharps are very good quality lcd's. i used to lan with a laptop and, even though it's ghosting was pretty bad, i got used to it and it didn't take away from my mad skillz.
i guess the one thing i miss about my crt where the high refresh rates. but it's hard to even say that becasue lcd's don't flicker at all. so 60hz on an lcd looks smooth as silk.
I have a phillips 15 inch LCD and I notice no ghosting and it has a response time of 40ms 20up 20down my room mate has a sony 19" lcd with a 25ms response time his however has major ghosting we think its because its alot bigger and just easyer to see.
15 is a good lan sized lcd anything bigger IMO is just to much I rather have a good ol CRT for the 17+ sizes I have a 15 for lans and my 21 for everything else.