A little Washington perspective here:
The state is certainly not immune to the world's fascination with points based on (seemingly) big wood, ripe phenolics (inky color! round tannins!) and a rich mouthfeel (based on glycerol due to higher alcohol)...and Syrah has been a part of it. The heat units and light (sun) intensity in a desert climate combined with a grape heavy on phenolics and sugar certainly adds to the potential for overblown styles. However...
The saving grace Washington has will always be its perceived alcohol and overall balance based (mostly, though not solely) on the acid generated by one of the most dramatic diurnal shifts (up to 40 degrees Fahrenheit on average during the growing season) in the wine world. Combine that with the renewed appreciation in the press for "cooler" climate versions of this grape and more folks felling confident in producing a Rhone-esque version (like Gramercy, Bunnell, Waters, Seven Hills, Otis Kenyon, Va Piano, Cougar Crest, Buty - try their Peter Canlis Cuvee against a Cote Rotie blind and see what ya think, Betz, Hedges, Owen Roe) and I think the region will realize some amazing juice. Even so, the richer styled wines (like K Vintners and Cayuse) with the huge extract and bigger mouthfeel can still capture the meatier/floral/peppery side even at 15 plus alcohol based on the diurnal shift.
At the moment, Walla Walla Valley, Red Mountain, Wahluke Slope and Yakima Valley have shown great promise with Syrah grapes. Vineyards like Boushey (*** is one of the top Syrah growers in the country, bar none), Ciel du Cheval, Red Willow, DuBrul, Les Collines, Lewis, Seven HIlls and Pepper Bridge are all amazing sources of balanced grapes. I am currently writing an article looking at the various AVA's and what they might bring before viticultural/vinification techniques take hold, and will share an abridged version for the GuildSomm.com site.
Will Syrah ever compete with Cabernet for popularity? Doubtful, but no one thought Pinot would smack Merlot upside the head, and lookee here! Will Washington ever be seen as one of the top regions in the world for the grape regardless? Most definitely. For those of you able (a great challenge, as Washington state continues to build its national presence but lags behind California - though probably not too far behind teh smaller producers mentioned by Geoff and company), I highly recommend a comparative tasting with Australia, California, the Rhone, South Africa and Chile. In a very short period of time, with relatively very young vines, Washington's best (!) Syrahs have established themselves alongside the upper tier. Maybe not quite Chave Hermitage or La Landonne...but, not too far behind.
I was a huge fan of Thackerey and Phelps and Dehlinger in the late 90's/early 00's. I have yet to smell a better New World Syrah than the 06 Arnot Roberts Sonoma Coast (forget the vineyard) - and also enjoy the Ramey, Copain and Ehren Jordan (name now?) work these days. If you do too, you will certainly dig some of the Columbia Valley efforts from Washington's best producers - and I say that as an MS who loves wine, not the Washington Wine Commissioner Education Director.