As promised, I wanted to report my experience with my Spike Brewing kettle. I got the 15 gallon w/ 1 welded port (SS ball valve). It arrived late last week and I finally got around to brewing with it after work today. My boil is currently about 35 minutes in and so far everything has worked just fine.
The weld seems strong on the port. I attached the valve and nipple with teflon on the threads, no leaks so far. I'm doing a 5.5 gallon batch on the stove-top and it's producing a way more even boil than my old 8 gallon canning pot ever did. I'm able to stir the wort without losing a boil momentarily.
Overall I'm very happy with the pot. There's not really much else I can say. It works as advertised and as far as I can tell you can't beat the price for a SS welded pot.
Edit - 2 more things. The handle on the lid gets pretty hot, so watch that. Also, the boil off amount seems to be way better (less) than my previous pot. My 8 gallon canning pot would boil off 1.5 gallons easy, even with a pretty mild boil. This has boiled off about .75 gallons in 50 total minutes so far of a good boil.