It may be a good product, but I don't think its a sales success. its supposed to be Weber's version of the BGE, at the pricing of the BGE. However, i don't think it ever got the cool factor that the BGE enjoys, the Weber doesn't have any buzz and honestly it needs it to sell at these kind of prices.
I find the Summit charcoal more appealing than a BGE and it would be cool to have, but I was never in the market for a BGE and spending that kind of pricing for it. Frankly it would have been nice at twice the price of an 18" WSM or performer as I could see it replacing both of those. I could honestly see myself with just a Summit stand alone (not grill center) as an alternative. But A) I have the WSM and Performer, and B) I haven't been using charcoal enough lately to the point of contemplating getting rid of the performer, to not have it rot in my yard.
I also do think its a market they should be in. However, I think that the price points are just an excessive jump from their normal charcoal line. $329 for a 26", $439 for a performer to $1499 the the Summit. Its a 3x+ jump to get to teh Summit line. What that tells me in my uneducated guessing, is that they're not looking for people to be upsold at all. They're going after a completely different class of customer.