I am by NO means a professional... But here's my advice anyway!
I bought upper body armor this year from a company called Demon. FlexForce X D30
The jacket I got is very similar to that one, MSRP was $140 and I paid $100 or so with a store discount.
I'm not saying there's anything wrong with the armor you found, I'm just not sure I'd want to spend $335 on just the upper.
I've heard great things about the lower armor, haven't heard anything about shin/knee pads or anything.
As far as my experience with the upper body armor, it's been great! For the first day or so it felt weird, felt like I couldn't flex my upper body as well. I must have got over that because I feel better than ever now. I've had a couple falls backwards on my back, and the spin protector held me off the snow while I skidded down until I got my board back under me. I also had a weird accident where my elbow jammed into my rib cage and it knocked the wind out of me. I was pretty sore but able to keep boarding for the rest of my trip (another three days) it could have been much worse without it.
I do find the armor keeps me much warmer than I used to be. I have a microfiber base layer underneath, and recently I've been too hot on the slopes. I may start using the spring jacket for my mid winter stuff, and keep the winter jacket for -30 degree days. In full on spring weather I plan on just wearing the armor as my jacket.