I haven't tried one on tenor, but my experience on clarinet and alto suggest that using a strength that's about right (i.e., not too hard) leads to very flat high notes. I thought it might just be me, but then I saw the video below, where a professional clarinetist plays the Venn reeds vs. cane (Reserve Classic, I think) and you can hear her go way flat in the altissimo on the Venns. She also suggests that the next strength up was essentially unplayable for her.
I've now tried a second-gen Venn on clarinet, so I figured I'd add another data point here. I tested a Venn 3.0 on both a Vandoren Masters CL4 and a Backun-Hawkins Vocalise G, with a Rovner Dark ligature. The CL4 is my backup mouthpiece; the Vocalise may be my new primary mouthpiece. My previous primary mouthpiece, a D'Addario Reserve X5, lost its cork after repeated use on the tighter barrel of my new clarinet. It's on the shelf until I get it recorked. But the Vocalise is pretty similar in feel to the Reserve, so I didn't have a great deal of mouthpiece adjusting to do.
I have mixed feelings about the Venn. Its tone is pretty good; perhaps a little brighter than a Legere Euro Cut's, but also, as many players seem to observe, slightly more canelike. And it's clear that D'Addario was trying to replicate the qualities of a classical reed; the clarinet Venn is no honker. Resistance and feel: also pretty good, for most of the range. But a big drawback is poor altissimo performance, which surprises me because I've found the Venn for alto sax to have good high-register response. The clarinet Venn basically craps out for me at high E, on both mouthpieces. It's very weird -- I have to change my embouchure to compensate and keep moving up the scale. Such an adjustment is not required for me with a Euro Cut (3.25 or 3.5), cane (Reserve 3.0), or Forestone Black Bamboo (MH). In fact, it's never really been required before; typically, going from high D to high E is sort of automatic. I suppose I could get used to having to finesse the reed at this point, but it would be annoying not to be able to play the way I always have.
I have not tried a Venn 3.5, so I can't say whether its performance would be similar.