Diamonds are my birthstone and my favorite gem. I like the fact that they are a very strong gemstone, and they sparkle with all colors of the rainbow.
I own all quality ranges, and yes, I prefer higher clarity and color, but I have purchased Affinity jewelry that I enjoy wearing (usually Affinity is minimum H-I color, I1-I2 clarity). Every once in a while QVC has used higher quality stones, SI, or G color, etc. They sell one ring that even comes with a GIA certificate.
Most inclusions are not easily visible to the naked eye.
Diamonds need to be cleaned constantly as just a little bit of dirt or film will limit the sparkle. Warm water, a toothbrush and mild liquid soap can really make the difference if one lacks jewelry cleaner fluid.
For regular daily wear jewelry it is fine to have the QVC quality level, as long as the stones are large enough to be fully cut. My main concern is often QVC uses single cut stones, or too many smaller stones with weak prongs that will allow the diamonds to fall out easily.
Judith Ripka and JAI use the same quality diamonds in their QVC jewelry.
Most major department stores sell similar level quality. ShopHQ uses a higher quality diamond overall now--G/H and SI for most vendors.
The prices rise substantially for higher diamond level. Additionally, there is no strong resale value for estate jewelry unless it is from a famous designer like Tiffany.