You might also consider Integral Designs' North Twin ($210; www.integraldesigns.com). It uses PrimaLoft for insulation, and most readers know I favor PrimaLoft due to its very soft, down-like feel. The North Twin is technically a ten-degree bag, but that's a very conservative rating and Integral Designs makes very hardcore gear. I wouldn't hesitate to take this bag out in the winter, and one can always pack along a vapor barrier liner (many modelsthey usually cost around $30) for a lightweight add-on that lowers the rating below zero. Weight is three pounds, eight ounces.
An absolutely traditional synthetic bag is Mountain Hardwear's 3rd Dimension ($220; www.mountainhardwear.com). Polarguard Delta insulation wrapped all the way around, contoured footbed, full hoodit's a bombproof, well-tested design. But it still has some good design touches, such as an expandable draft tube. You can open the draft tube up for more room and ventilation in warm weather, close it down for cooler temps, or open it and add another layer inside the bag for those minus-ten-degree nights.
Take a look at these and see what strikes your fancy. They're all good bags.
More sleeping bags reviewed in Outside Online's all-new Sleeping-Bag Buying Guide.