I just posted this in another thread. Sort of a "1 month later":
I put a set of the Helix Stainless Steels on my Jaguar about a month ago. They are definitely a roundwound variant.
Straight out of the package, they aren't particularly bright. However, they are very articulate, with a certain sweetness to the midrange (possibly due to the increased amount of wraps). Warm for a stainless string, but a different warmth than rotos. Lows are tight and fairly throaty.
For a stainless, they feel relatively smooth. But I wouldn't say they are smooth feeling strings.
They also feel quite balanced in tension. Overall I'm pretty happy with them, but the novel winding doesn't seem to increase their life. 3 or 4 weeks of moderate use and I feel like its already time for a new string. Rotos last longer than this, for me.