I think it is fair to say that the CL community is divided on whether or not relying on TCO is idiomatic.
replyI prefer to write my state-machines as transitioning with tail-calls, and I do get called for it. It's relatively easy to switch something written in that manner to using a loop with a trampoline, so I do so when my collaborators request it.
I wouldn't argue about things that are a matter of taste normally, except that I've had the experience where I've turned down optimizer settings in order to debug some code better and then the had stack overflow.
replySigh and yet it continues to be true. You can make a pragmatic decision and rely on tail call optimisation for your specific case, but if you are writing a CL library, then it is not idiomatic to use recursion in the same way that you would for Clojure or Scheme.
replyEven with SBCL, for example, it doesn't have tail-call optimisation for all architectures at all optimisation levels.