I would agree with you for the most part, but not completely.
Chevrolet does a good job competing with the companies it is supposed to, Ford and Dodge, as well as Toyota and Honda. I would agree that they have a lot of models that need to be trimmed back (in terms of variations) or completely cut all together. They really need to get rid of the SSR, Uplander, and Aveo as they neither sell well or really ad anything to the Chevrolet lineup. Word is that the introduction of the Camaro will also bring in a RWD Impala and Monte Carlo, which would be placing the two former W-Body cars in direct competiton with the Charger/Magnum from Dodge. Trucks are something that Chevrolet has gotten really good with, and my only complaint in that department is how stupid the Trailblazer EXT is, and that it should be cut completely. I'm sure a new version of the Trailblazer is on the horizon, so that problem may be faced sooner than we think.
Pontiac is indeed placed as an Acura compeditor as you had said before. As the affordable yet sporty cars in the GM lineup, they now slot between Chevrolet and Saturn in the updated product lines at GM. If anything, Pontiac only needs to ditch the Torrent and the Montana, as they too are slow sellers and generally dont do much for the Pontiac line as a whole. As for the future, there may be a replacement of the GTO by the Firebird (possibly, word was that the GTO will dissapear after 2008), and if the W-bodies go RWD with the Camaro, chances are the Grand Prix will follow along with the Impala/Monte Carlo. Pontiac does a good job of injecting plenty of sport going up to 8/10s and offers a good ammount of value in their vehicles, but they still have a little more work to do if they want to match the 10/10s cars available at the Acura dealer.
Saturn finds itself in somewhat of a two-faced state at the moment. While they continue to offer lower-level vehicles a-la Ion and L-series (maybe they stopped making that car...), the VUE and Relay are slotted pretty high in the GM line. With the revamp of Saturn currently under way, GM had said that they want Saturn to continue to be a youth-brand, but have the ability to compete with higher-level Hondas, Toyotas, and the lower level Lexus, Infinity, and Acura options. The new Aura (baisicly the new Vectra) has been set up as the bold new car to turn Saturn around, along with the Sky (the American version of the Opel GT), and the Outlook crossover (see Buick Enclave). I dont know if Saturn plans to completely ditch all of their affordable vehicles, but they should be the ones selling the minivan, not Chevrolet/Pontiac/Bucik.
Buick, its a tough call for Buick. Their purpose has been changed now that Oldsmobile is gone, as Buick has been clasified as the Lexus and Chrysler fighter here in the US market. Cars like the LaCrosse and Lucerne are great at what they do and IMO are better than many of their compeditors. But having Buick sell the Terraza, Raineer, and Rensezvous is just plain stupid. Buick needs to go back to the old days, and see what is missing. They need to be the "poor man's Cadillac" that they once were, while also offering good "everyman lux-models" that cars like the Regal and Rivera once were.
Saab has lost it's "Saabiness," I'll give you that. Although the 9-5 is still very much a Saab product, the 9-3 has become a mish-mosh of Saab and GM parts, and it just isnt what it used to be. On the same tolken, the 9-2X and 9-7X should be having the Saab founders spinning in their graves... They dont do much to hide the fact that they are heavily based on other vehicles, but they have done a good job of giving them a Saab-like personality. But it is true that Saab needs a small car to compete with the Volvo S40 and BMW 1-series, and an SUV to compete with the XC90 and X5. The problem is, Saab doesnt have the resources to make the cars and trucks on their own anymore, and they have to dig though the GM parts bin to find what they need.
Cadillac is doing the right thing. They build cars people of all ages and demographics would want, and they have done a good job of making them compete greatly with BMW's, Mercedes-Benzes, etc. If there is any complaint about what Caddy is doing wrong, they need to fit the 469HP version of the 4.4L S/C V8 under the hood of the XLR instead of the 444HP model, and they need to do a better job with the interiors of the cars.
Hummer, well, they are just going to have to be Hummers. As the top-line SUVs in the GM lineup (besides the Escalades), they do a pretty good job of offering a good ammount of luxury and utility at a somewhat (somewhat is open to your own call there) affordable price. My only problem with Hummer is that they dont cover a wide enough range of products to compete directly with Jeep and Land Rover. The H1 Alpha obviously sits atop that heap, but being that the tuck hasent been revised in such a long time, it has been far surpased by the Range Rover and Cayanne as the SUVs of choise when it comes to lux-off-raoding. The H2 plays a similar role as the H1, but does a far better job at doing so. But even only a few years old, the design seems dated, and needs an improvement...Hopefully a new GMT900 version is on the way soon... As for the H3, it just hasent lived up to the expectations that everyone had forseen. While they are selling pretty well, they lack engine power, and should have utilized the Vortec I6 as opposed to the I5 that is underpowered for such a heavy vehicle. However, they need a sub-H3 model to compete with the Wrangler, which could easily be done. Modifying the current chassis that underpins the Colorado/Canyon, they could use a mish-mosh of parts from other trucks to make a compotent off-road vehicle, and using the 4200 I6 out of the Trailblazer, they could match the new 3.8L V6 in the 2007 Wrangler pretty easily.