I've not had any luck with LXDE on Mer 0.15, it might be something to do with Xomap instead of Xorg, system boots after installation but hang's before gdm. I've had quite a few re-installs of 0.15, I get the progress bar hanging a lot. Time to re read the release notes.
I'm still using Mer 0.14 with LXDE which works great. Just as a side note, the LXDE faq ( http://wiki.maemo.org/Mer/Documentation/LXDE ) does not mention the setup of libgtkstylus.so to enable right mouse click, I followed an old post (cannot find it at the moment) "create file /etc/X11/Xsession.d/98x11-gtk_stylus and write there simply export GTK_MODULES=libgtkstylus.so