Figured I'd post what I've learned so far, in case it might be of use to any
others.

Got my Weber Summit Silver B gas grill yesterday. Was a floor display
model, already assembled, for $699. Great price, as brand new is $899-$999.
Has a couple of dings and a few scratches, but no big deal.

As this is my first "serious" grill, not quite sure what to make of it all
just yet. I like the four burners and the side burned (useful for reducing
sauces or making bastes, etc), and the metal body of the grill itself seems
quite sturdy. Seems to have a good thermometer and I like the flip-up
shelves - they seem quite durable, useful, and have a reasonable look.

As far as nits to pick so far:

One thing that I don't like, and didn't find out until AFTER I got the
grill, was that this is a new model for Weber, and as such, they have few of
the neat accessories that will fit it. It comes with stainless steel
cooking grates, which I suppose is all good and well, but I want the enamel
coated cast iron. BUT, they don't make them for the Summit Silver. What I
found is that you can use the ones that fit the Genesis B and C line (which
also fit the Summit Gold, you just use three instead of two grates), but
with just two of the grates, it leaves you with a four inch gap in grilling
surface. I ordered a single grate from Weber and am going to cut a 4 inch
section to fill it in. I also don't like the warming rack, as it is too
damned small to fit anything other than a few hot dogs. I want to be able
to put a roast up there if I want. Looks like I'm going to have to modify
another company's rack, or get a welder and get to work. I have noticed
that the electric ignition on the side burner doesn't work, as the electrode
doesn't sit up high enough in its mounting for the spark to reach the gas.
I had to shim it out with a piece of wire. Not sure if this is a result of
assembly at the retailer, or a Weber design issue. I think the unit would
benefit from something like a spice rack in the front, or some similar rack
attachment. The shelves are neat, but I find a rack to be more useful for
beer, spices, etc, as they are less likely to get knocked over. Not sure
what I'm going to do with the cabinet on the bottom, as it's one big open
space behind the doors - perhaps a shelf or rack inside would have made
better use of the space? Additionally, I have found customer support to be
spotty so far. I got one guy on their grilling hot line that seemed to be
pretty savvy, but the two women I spoke to in customer service were not as
well informed as I might have expected. They were courteous to be sure, but
not all that useful in answering my questions.

I baked the grill out for about 20 minutes, to make sure I drove off any
film, gunk, coatings, etc, left from the manufacture. It did smoke a bit,
and reached about 575 deg F in about 15 minutes (which is the max temp the
customer service woman said it would reach). Seems like a decent
temperature maximum. I also turned off all but one burner and turned the
remaining one to lowest setting. This resulted in a steady 200 deg F
temperature, which is just what I was looking for, as I sometimes use the
grill for low temp cooking.

Overall, the grill seems ok. Have yet to cook anything on it yet, so I may
be much more pleased or much more disappointed with a few dinners tucked
under my belt. I saw a Vermont Castings grill today at Home Depot, and it
seemed to have EVERYTHING I wanted, and for less money ($599, assembled,
new). Looked like coated, cast iron grates, 4 burners, good cooking area,
decent sized warming rack, thick, sturdy metal construction, spice rack,
cabinet below. I went with the Weber in large part because of the
reputation, likely availability of replacement parts and accessories, and
the good price. Hope I don't find myself pining away for something else.

Will keep you posted.

Paul