I believe others discussed it a bit here, hope you find it helpful
http://forum.brillkids.com/product-partners/tweedlewink-dvds-question/I found that quality is OK for watching on our computer screen and is a bit on a low end side when we try watching it on the larger screen. I think it is the matter of the format ( it does not look like they use HD, and nowadays everyone is used to HD), but we just make do with it, as content is definitely worth it.
Bit by bit I am creating my own lessons in LR courses, which eventually would replace TW use for me altogether (isnt LR course creator an awesome tool?!), and would allow me more variety and flexibility ( and my own quality images). But for the ready made program I think they are definetly worth it.
And I also wanted to mention -- if you do have any concerns about quality, you can contact TW directly, they have nice customer support and I found that they always answered questions in timely manner. Perhaps there is a problem with your particular set, or many be there is a need to put a certain setting on your regional player? I am sure they would be more then happy to help you!
Hope it helps. And welcome to the Forums!