I have a Shenandoah Quilt. It seems nice for the two times I used it. Both times at the bottom end of it's temp rating in the low 40s. I was comfortable, once in a bivy, once not.
I believe I've read posts of yours where you mention modifying gear. If you can sew, I'd recommend making your own synthetic quilt. Using Tim Marshall's Quilt calculator, and the assumption that one layer of 2.5 climashield is good down to about 45 degrees, you could make a quilt that is 3-4 oz lighter than the Shenandoah and good to about the same temps. Materials would be maybe $90-100 on Thru-Hiker, I believe.
The Shenandoah is great though. My problem is, I picked it on Gear Swap up 3 weeks before I lucked into a Nunatak Arc Specialist on Gear Swap. The Nunatak is good to 32 degrees and weighs 16oz. The Shenandoah is good to 40 and weighs 15oz. Problem is, I live in the Northeast now and even venting, the Specialist is too warm in the summer, so I'm keeping the Shenadoah for the time being for summer and as a layer for winter camping.
For the Sierras in the summer, a 32 degree seems ideal to me. Not so warm I can't vent, and can handle those unpredicted temperature dips(down into the 20s with the Montbell UL down Inner parka I'm sure you'll be carrying). If you want a great, light 3 season quilt, maybe go for the Arc Ghost, narrower and lighter than the Specialist.