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!

Which type of look/operation do you prefer? In those openings, you could really go either way, or do a mix of both. That is fairly common as well... The advantages of sliders would be a lower price (less total units), and you would gain additional glass area. On the downside, slider are generally leakier than double hungs, however you will have less lineal feet of sash and weatherstripping with the sliders, meaning less area for potential leakage.

Get a holder for single edged razor blades. Many auto parts stores have a type that has blade storage in the handle and a long shaft. I like that type better than the fold away metal holders. Use the scrapers as soon after removing the tape and when the finish has started to set. Material will have a tendency to stick to the blade of the razor. Getting it off safely can be done by having a rag handy. Lay the rag on a flat surface, hold the far end, and drag the blade away from the hand to clean.

@cpartist - Wow, I think we agree on something... I don't think my architect had muntins in mind, because I did not see them on any of his exterior elevations. I feel like the muntins will definitely tip the house towards the prairie style, which I think would cause us to choose a more earthy/older feel for the interior decorating and finishes. Going without the muntins would instead tip the house towards modern, and have a newer, brighter, more sterile feeling interior. My wife and I are the outdoorsy type, we like camping, hiking, and other outdoor activities. We still are drawn to the clean modern look though...