A lot of the requests on this forum are superfluous (like background customization and facebook bindings), and will only serve to complicate the code of this important program. Maybe you can charge people for that stuff, and otherwise keep it simple like it is.
There is just one thing I think it is missing:
An option to bias on/off to display certain parts of the tree.
it would really help to keep a complex tree sane to visualize, and to print out.
(Also, it probably should save to the local cookie and not to the tree itself, to avoid any possible social ramifications for it's use!)
Thanks for making this great geneology tool!