OK, so, I got my Firelite 550 and was able to compare it side by side with the old 500. And, I think this one's a keeper!
Like Ben, I prefer the new design to the 500. Here's why:
-I can easily boil a full 2 cups without boiling over.
-The slightly larger dimensions allow the handles to fold more flushly than the 500. On the 500, the top of the handles could slide up and hit the top rim of the pot. The 550 has more clearance so this doesn't happen.
-the 550 has an indented rim on the bottom into which my potstand fits perfectly adding more stability.
-lighter than the 500.
Here's my overall rating:
Ergonomics: A+
I especially like the indented bottom of the handles which allow you to slip your ring finger under to hold the pot more securely. Plus, with my tea light stove, neither the pot handles nor the lid handle get hot.
Durability: A-
As Ben has already pointed out, the thinner walls make the pot slightly less durable than the 500, but I would deem it perfectly acceptable. There's always a trade off in weight savings and only careless people would crush it.
Workmanship: A-
Overall the pot is well constructed except for some rough edges around the bottom fold of the outer rim. Again, acceptable and doesn't affect performance at all.
Compactness: A++
Even though it's a little bigger than the 500, it's still very compact and will save space in the pack. Plus, there's still enough room inside to stow my stove, pot stand, and windscreen.
Versatility: A++
Absolute perfect size for both a mug and pot. Seems to be a better fit than my Snowpeak 600 for the same application.
Efficiency: A+
The thinner walls shaved a full 2 minutes off of my boil time!
So, after the long saga, I've decided to make this as my new "go to" pot and fully recommend it.
I guess the long wait was worth it.

