I've tried to use R to fit some longitudinal models, mostly via
nlme packages. However, it seems that many standard models are lacking, such as antedependence models or factor analytic models for covariance matrices. These models are readily available in SAS.
Would anyone recommend other packages for the job in R? I don't really care if I use to work in a frequentist or bayesian world as long as I have more modeling flexibility. I would also be interested in doing that in WINBUGS/JAGS.