Lower response times are preferable. My NEC LCD has a response time of 16 milliseconds which is quite enough. Apart from gaming, this specification is very important when it comes to video playback, particularly DVDs.
However, since you seem to be more focused with flash and regular graphics, I wouldn't worry about shooting for the lowest possible response time.
As an aside, response times, or "refresh rates" as they are technically referred to, is the amount of time it takes for an LCD monitor to send a signal from the upper left most pixel to the lower right most pixel and then send it diagonally back up to the upper right again. The movement is done in rapid horizontal lines and ends at the bottom right pixel and is subsequently shot across the diagonal of the screen. This time last year, most LCDs had refresh rates of about 22-25 ms; I was lucky to find a good deal on my 16 ms NEC monitor.
So it seems Murphy's Law may still be applicable to the LCD market.
Also make sure you check out the monitors in a side by side comparison. The quality of the picture is unique to each display, as well as the brightness and contrast possibilities. If you're going to a BestBuy or CompUSA, remember that the signal is being split over dozens of monitors and is therefore going to appear significantly less satisfying than it will be when your computer sends one pure signal to it.
