First, much in the same way that the Columbia Valley is synonymous with winegrowing in Washington, so, too, is Ste Michelle Wine Estates (SMWE) with wine making in Washington. A colossal 60% of production comes from this family of wineries which now includes brands from across Washington, Oregon, and California. Most prominently from Washington are the Château Ste Michelle, Columbia Crest, 14 Hands, and Two Vines brands. With such a dominant presence, the remaining 40% of market share is split up between the balance of wineries. This gives you an idea of the size contrast between the 8000 pound gorilla and the 800-ish other wineries.
Side note: There's a little over 50,000 acres planted to vines in all of Washington State's 71,000 square miles. Napa Valley has 45,000 acres planted in 1/100th the land mass.
Second side note: Large does not equal evil, or even bad. SMWE, like Gallo in California, continues to increase quality at many price levels while holding pricing more or less even. But they're also vulnerable to the same temptation to dilute quality while holding prices steady. Bottom line - for real drinking value at the lower end of the price spectrum, look to the big labels. For a big step up in character (without a huge step up in money), explore the variety the state has to offer.
While the arid climate and complete reliance on irrigation help make for the perfect winegrowing laboratory, it is not without its vulnerabilities. Long growing days and mild temperatures can translate to high sugar content without full phenolic ripening. (If you're not quite sure what that means, you're not alone.) Once grapes are harvested, those high levels of sugars create their own challenges in the production facility. Volatile acidity is a real threat that can impart acetic acid aromatics and flavors (think vinegar.) There are apparently a handful of high end wineries where this is a serious problem, but the mainstream producers seem to have this well in hand based on the consistency of quality in the more moderately priced bottlings.
As is the case in other winemaking regions around the world, there are a number of winemakers in Washington state who are the eschewing the populist trend that favors ultra ripe, extracted fruit in exchange for more subtlety. Gramercy Cellars and the Owen Roe family of brands (Corvidae, Sharecroppers, etc.) epitomize this approach, yielding bottlings with much more lean and savory character. The Gramercy Cellars syrah is a dead ringer for the northern Rhone. Be on the lookout for those labels if that's your bag.
Finally. while the Columbia Valley is the largest umbrella AVA and home to almost a dozen sub-AVA's, even the smaller (and higher quality) sub-AVAs tend to label their wines as Columbia Valley due to name recognition. The story goes that, while insiders recognize and champion the quality coming from the smaller sub-AVA's such as Red Mountain, Wahluke Slope, and others, Columbia Valley name recognition still trumps all. Marketing curiosity aside, the astute consumer will look closely at the labels front and back for clues on sourcing.
To sum it all up, I will simply repeat the most valuable advice I can offer: seek out merlot from Washington state. Big syrahs and cabernets get all of the headlines and points, but the taking experiences in the value are to be found mostly with merlot at almost any price point.