Hi there. 

I'm trying to use the \only<> command to produce a beamer presentation but it seems that org-beamer filters out this. I've tried it in many different ways, and didn't get the desired effect. 

Particularly, I've tried the obviously wrong thing:
#+STARTUP:      beamer
#+LaTeX_CLASS: beamer
#+LaTeX_CLASS_OPTIONS: [smaller, presentation]

* Foo
** Slide 1 
\only<1> {
***  Block1     :B_block:
     :PROPERTIES:
     :BEAMER_env: block
     :END:
     - bla11
     - bla12
     - bla13
}
\only<2>{
***  Block2     :B_block:
     :PROPERTIES:
     :BEAMER_env: block
     :END:
     - bla21
     - bla22
     - bla23
}

Which obviously break-up. And I also tried what I believe would be a nice syntax for this:

* Foo
** Slide 1 
***  Block1    :B_block:
     :PROPERTIES:
     :BEAMER_envargs: \only<1>
     :BEAMER_env: block
     :END:
     - bla11
     - bla12
     - bla13

***  Block2     :B_block:
     :PROPERTIES:
     :BEAMER_envargs: \only<2>
     :BEAMER_env: block
     :END:
     - bla21
     - bla22
     - bla23

Apparently the parser just removes the "\only" and interprets this as <1> and <2>. The resulting latex is exactly the same as if the "\only" wasn't there.

Is there a way to use the "\only<>" overlay in a clean way? 

Thank you very much.

---
Rafael Calsaverini
Dep. de Física Geral, Sala 336
Instituto de Física - Universidade de São Paulo

rafael.calsaverini@gmail.com
http://stoa.usp.br/calsaverini/weblog
CEL: (11) 7525-6222
USP: (11) 3091-6803