I think the removable ones have improved in quality and appearance over the years, but not alot of people use them anymore. Yes they do help with cleaning the glass, but you still have to clean the grids too. This is why alot of people are opting for grids between the glass (GBG). You get the traditional look of mullions without the dual cleaning required--just spray the window, wipe clean and walk away. I'd be willing to bet this is the type of window many of your friends have that you mention really not noticing the difference in.

Pricewise, there is a considerable difference between the styles. From our window shopping experience, the least expensive is no grids, then GBG, then removable grids, then DL/SDL.

Alot of window salespeople may be assuming when you say 'permanent' that you mean GBG when what you're really referring to is called divided lite (DL) or simulated divided lite (SDL). That would explain why they are surprised. Most newer homes have GBG. Those homeowners who are going for a true period look typically install the DL or SDL. Older homes with old/original windows typically have DL as well.

Hope this helps!

While grids-between-glass and removable interior grids look the same on the outside because you see a single sheet of glass, I think the removable grids on the inside look a bit better on the interior of the house because you see the division over the glass instead of behind it, and since it is more three-dimensional that adds to the appearance.

I prefer simulated divided lights with the spacer bars in between for the energy efficiency + the look of a true divided lite, personally. Of course these are probably as expensive as true divided lite.

One of the issues with between the glass grids is the color limitation: unless you have a white or off white trim, throughout the house, the between the glass grid loses any sense of realism.A different trim color on the sash than on the grid only emphasizes what it is (or is not): because you would never intentionally paint the perimeter of the sash one color and leave the divisions white on a true divided lite window, which is what these other forms imitate.

Our old house had the removable muntins....I hated them. I didn't think they looked as good from the street, as the face of the window was flat and one dimensional. That is also why I do not like the between the glass ones, either. We have SDL in our new house, and I like them so much more. They are a bit more difficult to clean, but worth it to me.