To each their own, but I find your travel justifications a poor way to qualify the $450 annual fee. I only keep the card for the 5x points at my Benz dealer (the only spend I put on the car as I find MR points a poor value compared to so many other programs out there) and for the Amex Centurion Lounge access.
They reimburse you certain airline fees, automatically - I selected early bird check in for my Southwest flight and they saw that and reimbursed me with a credit within a couple of days. They also reimburse carry on fees and other things up to 200 a year
Next - they reimburse you the cost of the TSA Pre-check which allows you to bypass some of the security, and if you've stood in those long lines removing your shoes and emptying all your stuff out, you already know that's a winning thing. The cost is 85 dollars and it's good for 5 years but Platinum will reimburse that. (I'm planning to stop at our local center next week and apply for this).
It also upgrades your status at the major rental car companies. It's hard to put a financial value on this, as well as the upgrades at selected hotels, but it's a very nice perk.
It lets you into selected lounges as well. I just got my Priority Select card, and since my return flight was delayed, that would have been a nice perk had I had that card and there been a lounge handy.
If you are traveling for work, they should be paying for the baggage fees and early boarding. My $200 / year credit goes straight to gift cards, award booking fees, or change ticket fees which are reimbursed so I count it as a true cash. If you are not getting reimbursed for baggage fees you are still paying for it indirectly.
TSA Pre reimbursement is every 5 years - it is a great benefit but after year 1 (or even month 1 of the Amex Platinum) there is no monetary benefit. If you cancel the card you keep Pre Check.
Getting car rental status is very easy. In fact signing up for the Mile Point promo last year that included Hilton Gold, National Executive, etc for $50 would have been a better deal for you.
Most people signup / keep the Amex Platinum for a few reasons - especially with the recent loss of AA / US Lounges and no guests to Delta Lounges.
1) Status sign / bragging
2) Large signup bonus & first year is practically free by receiving the $200 statement credit twice (split over 2 calendar years)
3) Amex Centurion Lounge Access - this is why I keep the card. I also have the $450 year Citi AA Exec card for access to AA / US Lounges when I am not in DFW but the Amex Lounge is superior for when I am in DFW.
4) Need access to a large NPSL - but other Amex cards offer this for significantly less
5) Insurance on items they buy or travel
I will be curious to see if you keep the card when you are billed the $450 annual fee next year.