I am not a macro person (as in shoot small bugs) but I do use automatic extension tube. Cost around $70 from ebay including shipping. The good thing about auto is that I can take closeup shots handheld without manual focusing.
No degrading of IQ but you do lose some light depending on how many long is your extension tube. If it is too long and significant light is loss then the camera might not be able to focus automatically.
It's good for food pictures as you usually won't need to close up to the size of a single grain of rice. You can play with a variety of lenses instead of only the ones that suits the close up lens' filter size.
Extension tube comes in 3 pieces right? The pic above I used only 1 piece...so you can get even closer if you stack up the remaining 2 pieces.