Maybe it's just all in my head but when I had CSSU installed, I had little issues and my phone felt more slower. So I've reflashed fresh and now just run without CSSU and with power kernel v46 overclocked at 1.1Ghz. (which I was running before anyways) It's never been more stable and responsive. For the past month, I never had to reboot once except to dual boot to NITDroid.

Teeny weeny update. I reflashed both the emmc and root, but problems have started again. Conversations is unstable, e-mail is more flaky than usual, and today it even did a reset in my pocket (I noticed the power-on chime). Application manager was completely on it's knees, but when I reset the mile-long log full of errors and notices it worked again.

Time to try a second re-flash. But this is weird- this time around I stayed from installing extra **** just to test it.

agreed my biggest mistake was restoring apps but once i sussed that out its been good on battery and problems for months

i have mysterious problems every so often but if i reboot phone once ever 2 or so days and a full shut down weekly its quite good

i have the odd problem with conversations going stupid where it shows there not sending but they are,
i receive the same msgs twice or more
certain peoples contact names disappear and when i send or receive a msg and go back in its not there
but most of that happens when 1 contact is around the 15000 mgs mark

New update.

I think I'm on my 3rd complete reflash now. Yesterday the phone started acting up again - and now I can't even access the eMMC, and therefore almost no application or feature.
Smells like HW error - time to return it to Nokia... luckily we here in Norway have 2 or 5 years of warranty/claim rights for manufacturer faults on consumer devices.

It's all about the complexity of the OS. It's, of course, much less stable than iOS or Android, but do remember that these OS'es are designed entirely (from the kernel to the GUI) for mobile purposes.
Maemo, is entirely backwards to that position. It's a full desktop operating system, stripped down, not even for mobile purposes, remember that it has more computer-side functionalities than phone features. So it's more possible to break it up, and there are more possibilities that you can crash it (multitasking without limits has it downside).
So, TL;DR: Yes, it can be an unstable OS. But it exceeds the capabilities of ANY mobile OS to this date.

It's me again.

Just got a new N8 as a replacement from Nokia.... HW error and no new phones in stock to give me.

It's actually a lot nicer than my N97, but not quite Maemoish.

maybe ask for a N9?
from a SW / OS point of view, you'd have a good stand

Actually I was debating whether or not to deny the exchange and ask for an E7...decided it was not worth the hassle.
Anyways, there's an N9 to be ordered when it arrives so I guess I can live with this N8 until then.

(FYI, the e-mail client in Symbian^3 is actually very nice. Instant opening of e-mails - take that Modest!!! )