Scattershot thoughts...
<i>arnwyn</i>: As noted before, I can't say I disagree with your answer. At the very least, I'm now convinced that product stores and play spaces are separate businesses with separate customer bases. They're complementary at best, and one mistake store owners like me are making is trying too hard to combine them.
Your space description does point out a few more possible features: stereos, tunes (and special effects), soundproofing.
<i>Rel</i>: You've got an excellent point, but I don't 100% buy into "it's a better deal to improve own space" argument. People can buy home gyms, but lots of them prefer to go to a workout club instead. A lot of city-dwellers live mostly outside their apartments because they don't want to try to fit their friends in a studio apartment. (Which points out a problem for less urban locations like mine.

) Many product store customers are in your situation and don't want/need play space, but that doesn't yet exclude the <b>possible</b> existence of another customer base that can be developed.
As far as other customer bases go, it's worth noting that the heaviest users of our current space are kids and teens. Most of them have perfectly nice homes to play in, and they're here because they want to get out of the house.
BTW, we've experimented with a LAN in the past. So far it's the most expensive mistake I've ever made.

Other store owners have done very well with them, of course, but we quickly discovered that we couldn't afford to keep up with the technology folks had at home. FWIW, once you made the initial investment in a spiffy playspace I think it would be easier to keep improving it -- you wouldn't have to worry so much about a technology curve and obsolescence. Monthly improvement would have to be part of the plan, though.
<i>satori01</i> (and <i>eris04</i>): I can't believe it hasn't occurred to me before, but in addition to various terrain and dungeon stuff, I think a full suite of miniatures to borrow would be a must. As a GM who loves minis but never has any time to collect and paint them, I'd love to be able to borrow everything I need for a session from the library.
I guess the ideal is really for the GM to be able to show up with nothing but his notes -- or better yet, show up with nothing at all and have Jeeves hand him a printout or PDA with the GM's emailed-to-the-space notes on it.
(Jeeves can also suggest plots, help the GM plan the campaign, and fish impromptu backup adventures out of the library on demand. If we're fantasizing, let's think big!

)
<i>Mark:</i> LOVE the dry erase board idea.
<i>TalonComics</i>: If it makes you feel better, we've got lots of space and haven't really gotten it together yet. Whether we move or not, I've got to make some tough decisions over the next two years as to how to use our space better -- I want to be proud of our playing space and the profits it makes by the time our 10th anniversary rolls around, and we've got a long way to go on both counts.
I'd love to know what your bricks & mortar store looks like, by the way. I don't have any visualization of it at all, so I'm very curious.
cheers,