Last I checked, the N900's NAND doesn't have wear level. The eMMC (where MyDocs, etc, goes) does, but I've read people more knowledgeable than myself on here say that the NAND doesn't wear-level.

More over: Everyone on here who's ever said anything about multiboot other than the second poster has said that multiboot does flash the kernel.

When you boot into multiboot and select the OS to boot, it flashes that kernel image in place of whatever's on the NAND, and reboots. So, upon reboot, you're loading with the new kernel.

uboot on the other hand does not need to flash, because uboot can load a kernel image that's configured properly from ANYWHERE on the device. It's less intuitive and not exactly newb-friendly to make it work, but it's definitely better.

However, keep in mind that modern flash chips have like hundreds of thousands of erasable 'layers'. So you've got hundreds-of-thousands of writes, even without wear-leveling. If you boot into different OSs, say, ten times a day, that's still over 10 years before you kill your chip. So you shouldn't worry about it TOO much.

I always recommend uboot because I think it's more versatile and in the long run it will be better to have people switch to that, especially if a N900 newb-friendly version with easy commands like "run nitdroid" and "run meego" is made available. Which I suspect there will be, and soon.

Oh, the root access stuff - with rootsh downloaded, just typing "sudo gainroot" or "root" will elevate you to the root user, without asking for password. "su", I think, doesn't work the same way on the N900, if it exists at all. All other "sudo [something]"s ask me for a password, which is not the same password and my normal root one, or my user one, so *shrug*. I only once figured out how to set that password, and that was two reflashes ago and I don't bother, because I usually just use sudo gainroot anyway.