I bought this TV when it was on sale a couple of weeks ago. So far I have been completely satisfied, although it is quite a bit more reflective than the 32" Sony LCD we had in the living room before. We can deal with the reflections.
Now to answer some questions in this thread: it's a 720p TV at 1024x768 native resolution. Supposedly the missing lines of resolution are not as important because you can't see vertical lines as well as you can horizontal lines. Or something. And the HDTV consortium (or whatever) states that any TV that has 720 or more lines of horizontal resolution can be sold as a 720p HDTV. This thread has a lot of info about it:
http://www.avsforum.com/avs-vb/showthread.php?t=758937
My 32" Sony was 1366x768 and I have not noticed the resolution difference at all. That said, my only HD source is an Xbox 360. The rest of my sources are 480p DVD's. I have the TV hooked up with its component inputs through my Onkyo TX-SR703 receiver. I will hopefully get an HDMI-capable receiver soon and hook it up through HDMI. Also, being a bigger TV, we re-arranged the living room and now sit farther from the TV, so resolution is less noticeable.
Now, as to who makes the TV. It is a rebadged Samsung. The soft-touch buttons on the front bezel: Samsung. The remote control: Samsung shaped, with different plastic. The back panel: same design as a couple of Samsung models, but missing a couple of connectors.* The base upon which it sits, and the method by which it is attached: same as Samsung. So IMO it is fair to say that this TV was 100% assembled in a Samsung factory. But IMO it is better than a Samsung because it has a 2-year warranty and that warranty is through Best Buy, as Insignia is BB's house brand. If I have a problem, I can bring it to Best Buy, and they will have to deal with it. There's no rigamarole dealing with the manufacturer vs. the dealer -- it's cut down nicely. Not to mention, the price is lower than a comparable Samsung would be.
Now, I am usually a spec hound. If I were spending $1000+ on a TV, it damn well would be 1080p, have more inputs, be a big name brand, blah blah blah. $1000 is well into my "major purchase" range, and it would be a very considered decision! But at 42" for $400, you've got to cut corners somewhere and realize... it's $400. $400 is cheaper than many 32" TV's on the market. This TV meets my needs very nicely. It's got a great warranty (even better since I bought with Amex). Its limitations don't affect me and my situation (switching sources through a receiver, no 1080p sources, etc.). I would expect to see better deals on Black Friday, with all the Black Friday caveats (camping out, limited numbers, etc.).
*Note: Those missing connectors might be important, depending on your situation. There are (2) HDMI inputs and (2) component inputs, one of which is shared with a composite input. The green RCA connector for one of the component inputs doubles as the yellow (video) RCA connector for the composite input. So, you can have only 2 analog inputs at a time, only 1 of which can be composite. If you've got a lot of older analog sources, you will face a bottleneck.