A much needed discussion, thanks to the author of the OP for starting it. I am a very critical consumer, and this is no different with backpacking gear. I try and do a fair amount of research before nearly all of my significant purchases, and very often try and buy used or discounted when possible.
Once I got my first basic UL (under 10lbs BW) gear list finished a few years ago (circa spring 2011), I went out and put it to the test. I made a lot of mental notes and learned quite a lot on trips, then I would come home and do research.
I think it is also worth adding that after going UL I would say my overall experience of going backpacking/camping/dayhikes/etc. went from "good" or say 6-7 out of 10 as a lightweight backpacker (20lb-11lb BW), to "great" or say 8-9 out of 10. My section hikes in summer/fall of 2012 were "excellent" or around 9-9.5 out of 10. I am now in the process of just fine tuning each of my gear systems, mostly focus on the two most used kits: my spring/fall or 3 season, and late spring to early fall 1+ season. Looking to maintain or improve things in the realm of "excellent" or that sweet spot of around 9.5 or over, 10 of course not existing (nothing is perfect, there are no essences--my existential influences are revealed).
A good example was my changes in backpacks. I made a MYOG backpack that was 445g, but was fragile and not the most comfy pack to haul. I did a lot of research and then finally settled on a Golite Jam because it was cheap, tough, and got pretty good reviews. Bought it new because I didn't yet trust gear swap as an alternative marketplace--my skeptical nature now reveals itself.
Took it out on lots of trips, but in doing research on backpacks in general, I learned about lighter ones that got the job done just as good if no better than the Jam. Observed gear swap at and reconsidered it as a way to buy gear. Finally settled on a MLD Exodus that was slightly used and on sale here on gear swap. Took it out on lots of trips, it carried weight nearly as good as the Jam, and I actually liked it much better over all, with certain features I felt were better (such as the shoulder straps and minimalist design). The Jam is now my urban backpack, and is great at it, because it can handle a lot of weight from books, laptop, groceries, etc.
Next problem was that while 50 liters volume is good for me during some trips and seasons, it was far too much for other trips and seasons. I needed a smaller backpack to use on overnight trips and 1+season section hikes, and I had also cut down on a lot of bulk and weight in the rest of my gear list anyhow. Because of several specific factors I wanted to address, and because it was in my price range, I decided to buy a new custom Zpacks Zero. Took it out on lots of trips, and between that and my Exodus, I feel no need for any more packs right now--they satisfy all my present needs, but this of course could change.
So my gear purchases are pretty methodical, and I am not interested in collecting gear or hording it, but putting most of it to frequent use. I recently picked up a Borah Bivy on gear swap after much consideration on fine tuning my 1+ season gear system (355g total for full rain/wind/bug/critter protection using tarp/bivy/ground cover, plus flexibility of being able to use bivy in trail shelters) of and look forward to taking it out and seeing how things go. My hope and expectation is that I can improve my trail section hike shelter system and stay or improve on that sweet spot of a general 9.5 out of 10 experience out there :)
EDIT: fixed typos, as usual