I've been thinking a lot about putter design lately. I find center-shafted, non-offset putters easiest for me to aim and putt with.
I like that the sweetspot is aligned with the shaft. It makes sense to me. Contact feels much more solid.
The center-shafted putter is also easier for me to look at. Nice and simple. I find double-bend putter shafts to be disorienting, and most plumber-neck hosels make the face look closed.
The thing I like most about the center-shafted putter is that it makes it very easy for me to trace a straight plane line. I just keep the tip of the shaft pointed at the line throughout the stroke, though it does move off for longer putts.
As far as stroke type is concerned, I think I'm fairly SBST. It's just how I putt, there's been no conscious effort to avoid an arcing stroke. Opening and closing the face feels unnatural, so I just let the putter swing while making sure that the face angle stays perpendicular to the plane.
Lately, I've been experimenting with more of a side sadde stroke. It's not Sam Snead side saddle, but I'm standing more open to the line with a narrower stance and just trying to brush the ball to the hole. I have a 38-inch putter with a long grip that I hold split-handed, ala Happy Gilmore (I'm starting to think that movie may end up as one of the greatest golf instructional videos of all time).
It's been lethal on short putts, but I have to remind myself not to get too flippy with the brushing. Tracing a straight plane line helps.
As far as D-plane/swinging left is concerned, I'm content to leave that alone unless I really start to have problems. My stance is that if I'm rolling it well, there's a decent chance I'm already conforming to at least some of the D-plane imperatives.