Barbara, at her About.com Buddhism blog has a nice intro to the perennial issue of newbies and foreign (to them) forms in Zendos.
I figured that rather go into the "gentle dissuasion" that I was met with on my first visits to Rinzai Zendos (both in NY and in the Pacific Northwest) and its relative benefits, I think a more important point that needs a response here is this:
So much of Zen is practicing with the body. Zazen, shikantaza especially, is body practice, not brain practice.
The response I would have is that in my experience, in the White Plum Asanga tradition there really isn't the same kind of physical practice that there is in the Rinzai tradition; it seems to be one of those things that got lost in the mix when the Yasutani folks mixed Soto and Rinzai. To say that there is "especially" physical practice in the Soto tradition is basically I would submit might possibly be due to an unfamiliarity of the tradition in the Rinzai school.
I don't have time to go into it now, but there is actually a very different kind of physical practice in the Rinzai tradition relative to the Soto tradition; it's not empahsized less relative to the Soto school at all, in my experience. Part of it involves how to work with the hua t’ou; and the fact that koan practice is the furthest thing there is from intellection. Another major part of this physical practice is using the breath in a way that simply isn't taught in the Soto school; it comes in large measure from Hakuin himself.
I'll go into this more in an upcoming post.