Standard Definition is 480 lines of resolution. The television's panel is 1080p lines of resolution. Watching SD signals on an HDTV is a bit like zooming in too closely on a picture on your computer.
I'm not sure what constitutes "reasonable and acceptable" images, and I can't really argue anyone's perception, but standard definition is a lower resolution than what is designed for the panel. While technology is there to improve the upscaling of a SD picture, there's only so much clarity a television can add through processing the picture.
Digital TV doesn't equate to HD television, it just means the signal is comprised of 1's and 0's, rather than the analog wavelength channels. What would help most is High Definition.
And that difference is seen on the display. One suggestion I would make would be to go to your local retailer, and ask them to turn the TVs to a few Standard Definition channels or hook up a DVD player (not Blu-Ray) so you can view all of the televisions to see how they handle a SD picture. I would wager that the result will be similar to what you're seeing on your set at home. Not all retailers have access to Standard Definition signals, so if not where you purchased it, go to a retailer that can demonstrate this for you.
I recently got a samsung C610 for the sole purpose of watching cable TV. I am having blurry images, by such I mean shadowing around the images sometimes so bad that i can't even read out the smaller letters. The cable signal and installation have been checked by the cable provider and they're fine. The samsung service technician checked it out as well and apparently the TV is able to broadcast the HD channels perfectly with an HD box but little can be done for the remaining channels which are in standard digital mode. I find this quite strange as i know for a fact that even if the TV is HD one must be able to get reasonable and acceptable images even if they don't have an HD or digital box. That is a FACT!!I thought maybe the settings were wrong but the samsung technician dismissed that too. Pretty soon I am going to return this product as it turns out , it is not able to function properly with cable TV. Any suggestions before i do so?