[R-sig-ME] Julia vs nlme vs lme4 implementation of fitting linear mixed models

[W Robert Long]

What are the resources that compare how linear and generalised linear 
mixed models are fitted in julia, lme4 and nlme in terms of the how they 
differ in their implementation, and what advantages/disadvantages each 
has. I'm asking about the theoretical and computational issues rather 
than comparing speeds for any particular dataset/model.