Well, exact root of evil in Maemo boot problems is identified (I hope).

Maemo it seems relies on CONFIG_SYSFS_DEPRECATED in kernel. But android's vold (VOLume Daemon) can't work properly with kernels built with this option.

Now dualboot almost works (but android fails to mount sd-card). Still need more testing... And that's because I uploaded new kernel && rootfs.

Guyz, wifi is partially working (search fails, but ap names visible in wifi-manager). Can somebody carry out test for wifi on open (or WEP) access points?

Thanks.

links && md5sums:
http://newsycat.com/android/n900/zImage fa967ef065d18f007ea24607ba3c4138
http://newsycat.com/android/n900/android7.tar.gz 55ece4afed2d235d562288dda6d0505f
http://newsycat.com/android/n900/android.item 2971888b56778d152cb80973ec49695b

P.S. if something fails try...
1. change root device in android.item file (ITEM_DEVICE parameter. refer to bootmenu documentation and your logic)
2. contact me at #nitdroid. describe problem. I can't see (from my location) display of your n900 etc. in other words, I'm not telepath
So, as more information you give, faster I can help.