New version on official website for FF 4 Puntuado con 4 de 5 estrellas
There is a new version v1.72.0 (as opposed to v1.7.0 here) on the lastpass website that makes this addon fully compatible with FF4. Before I had problems with Lastpass windows and aero rendering incorrectly but the official lastpass download on the site solved that.
Beside that note, excellent plugin, I am very dependent on. The only con I can think of, is that this is by far my largest addon coming in at a more than 2 megs (4 megs uncompressed) so I am wary about Firefox bloat considering Firefox itself is only 8-9 megs (25-30 megs uncompressed).