I purchased this set to replace an old CRT model and have been blown away by the quality of the picture. Truly one of the best bang-for-the-buck models out there. That said, there are two common problems that people have experienced with this set and others in the Toshiba Regza series. I had both, but have found solutions.
1. CABLE REMOTE CONTROL INTERFERENCE
When the TV is in "auto-view" mode (the default), it emits an IR signal to measure ambient light, and adjusts the TV's backlight brightness accordingly. This signal can cause remote controls for certain cable boxes (in my case, a Motorola DCH6416 from Suddenlink) to work intermittently or in some cases not at all. From what I've read, remote controls for some other devices (satellite boxes, audio systems, etc.) can also be affected. The solution is simply to switch the TV from "auto-view" to one of the fixed modes such as "standard". Granted, this is not a perfect fix as you are disabling an advertised feature of the TV that you've paid for. Some others have reported that separating the TV and the affected device by several feet will eliminate the issue as well, although this may not be practical depending on the physical setup of your system. For me, disabling AutoView solved the problem and I'm satisfied with that.
2. AUDIO DISTORTION/ECHO USING HDMI INPUT
Search the web and you'll find this to be a common issue as well: after several hours of use, the sound can become distorted and tinny, with a buzzing sound and an odd "echo" effect. This affects the TV's own speakers as well as the signal coming from the set's audio output jacks. Toshiba has known about this problem for some time; from their web site (dated 3/26/10):
"To ensure the satisfaction of our customers and to maintain the integrity and quality of our products, Toshiba America Consumer Products, L.L.C. ("TACP") is posting this notice about the 40XV645U, 40XV648U, 46XV645U, 46XV648U, 52XV645U, 52XV648U, 42ZV650U, 47ZV650U, 55ZV650U, 46SV670U, 55SV670U TVs. This is not a safety issue.
Recently, it has come to our attention that users of a small percentage of those model TVs that we have shipped and are used in connection with a set top box via HDMI may experience a random audio echo while watching programming. If this were to occur, it would only be after many hours of continuous viewing and can be temporarily resolved by turning the TV off and on again.
If this audio echo is interfering with your enjoyment of your TV, please contact TACP Customer Solutions at 1-800-631-3811."
The permanent fix is to upgrade the firmware from ver 6.1.43 to 6.1.45 by downloading from Toshiba's support site at [...]. This admittedly is not for the technically challenged, as it requires downloading the firmware executable, extracting the contents to a USB flash drive, then finally applying the patch to the TV via a somewhat convoluted procedure. I initially had some problems, and it wasn't until I manually changed the directory structure of the flash drive to put the boot image file in the root (instead of a sub-folder as created by the upgrade installer) that I was able to get it to work. But then again, I'm a tinkerer with a fair amount of computer knowledge, and I was determined to figure it out by myself. Those not so inclined would probably find that Toshiba's tech support would walk them through the process, and I've even heard in some cases they will send you a flash drive with the patch pre-installed -- all you have to do is insert it into the TV's USB port and turn it on.
These two issues aside, I'm very pleased with this set.