So here's my opinion on the Swell.... While I can see why a lot of people would really dig the tone, it's not for me. I didn't jive with it, just very bland and generic sounding. It DOES do a nice tube tone when you dial in the right setting, but I expect more from a $300+ pedal.
These are not so much pro's and con's, but more like observations. Take them at face value:
1) I don't like the design of the interior. For a pedal to contain a fragile tube, it should be isolated and have flying leads to the board. Everything including the pots are mounted to the PCB except the footswitches. I'm never a fan of this type of construction and having a tube makes it even less desirable. I did notice after I did the demo, I opened it up and the tube had wiggled loose a little. I can only imagine if my foot came down the wrong way on the pots and cracked the board or the tube. It's a no-no.
2) I found myself wanting a full tone stack at every gain setting. It was either a little too much treble, not enough bass, boost or cut the mids, etc. A single passive tone control leaves a lot to be desired for the tweaker in me. Since all drive pedals have naturally occurring compression, better tone controls became a necessity rather than just a desire. At the highest settings and maximum compression, your tone controls on the preamp have little to no effect.
3) It did get a nice tone when I found the sweet spots BUT, it's nothing that I can't get with MANY other non-tube pedals.
Since so many people have asked me about the Swell compared to Darkglass, there is no comparison.
The Darkglass B3K and B7K still remain my favorite overdrives for bass, hands down. 
The Okko Basstard comes in a very close second. There really is no comparison for me at least, since these pedals are wildly different. I have a feeling the Swell might have become the flavor of the month.
