Nice list, well thought out. This year the PCT is playing out quite a bit differently than in 2009, mainly in the sense that snow is taking longer to melt out this year, for what it's worth. So keep in mind my comments reflect experiences from last season.
First, starting on May 21st, you will be hitting Southern California as things typically begin to really heat up. I would suggest that you carry more than the ~3.3 liters of capacity. There are stretches approaching 15-20 miles in Southern California where there was not any water available along the trail. The guidebooks you are using do point those out. At the most, I believe I had 5 liter capacity, although I seldom carried more than four.
On your headlamp, and I know I've mentioned this so many times that people are sick of hearing it - the eLite is a terrific headlamp for camp. Wonderful. But in my experience, it is at best a mediocre headlamp for night hiking. I tried, but ended up supplementing it with a much more able headlamp. Chances are that you will elect to hike at night, either to escape the heat of the day or perhaps you will need to get in the miles to make a post office before the weekend. I found that with the eLite the hiking was slower and much more exhausting because it had such limited range and required greater concentration on finding the trail.
I haven't met a lot of people who liked using the Go Lite umbrella. There were several who carried them, but the general complaint was the performance under breezy conditions. It was almost always hot and windy in So Cal. Something to consider, but I would carry a wide-brimmed hat for at least Southern California. YMMV.
The BearVault 450 is obviously limited in its capacity. What is your resupply strategy in the Sierra?(FYI - I was told last year that the hiker box (really drums) at the Muir Trail Ranch were fantastic - seems a lot of JMTers leave a ton of food behind.) Anyhow, it's around 90 miles between Kennedy Meadows to Kearsarge Pass, which leads to the towns of Independence and Bishop (you need to hitchhike in). Also, if you are going to climb Whitney (which I would recommend heartily), that is going to take a good portion of one day in this stretch. Something to think about.
A lot of people wore just shorts in SoCal. But when it is hot and sunny, you are going to go through more sunscreen than with pants. Just something to consider - plus pants do a better job protecting against a lot of desert plants. I had never hiked with pants (other than rain pants in my life) up to that point, always opting for shorts. I was glad to have made the switch.
If I had to do it again, I would probably have brought some type of gaiters with me to keep rocks and dirt out of my shoes in SoCal. The rocks and dust filled my shoes, which breathed well but as a result, also took in a fair amount of debris. My feet swelled pretty good in the heat, and by the time I reached Big Bear I swapped out my size 9.5 shoes for size 11.
The iPhone did not get good reception in many stretches of the PCT - this is more of a function of the network than the phone. I didn't use an iPhone but friends did. The AT&T coverage wasn't that good in many areas.
Finally, if you finish by, say, Oct 1 you will average just about 20 miles per day. This does not take into account any zero days or generally lower mileage days in the Sierra (certainly, I'd recommend enjoying the Sierra and not rushing through it like a bat out of hell - another reason to maybe carry a larger bear canister).
Best of luck to you! Enjoy the trail.