Dead easy indeed : just install Python !

Sports Tracker and Nokia Maps.

I see a lot of people comparing the two OSs namely application wise. That is not entirely up to the OS. A lot of good apps can be written for any OS.
The main thing here is to provide the ease of use. Maemo on N8x0 is still quite Linux guru oriented, and if Nokia wants it to replace Symbian, they need to make it much more user friendly, even if they upset the Maemo purists in the process. For a lot of things, one still needs to open terminal and do things manually, which is something not acceptable for an ordinary user.
The other important issue is of course OS stability. I had a few situations when I needed to reflash my N810, without any apparent reason. This is something that must not happen to ordinary users. The system needs to be bulletproof, as Symbian OS is today.
Thirdly, seamless application installation, since Symbian is quite good at this, and I guess apt based package manager will be able to provide this. I haven't been that informed on application manager in Fremantle, I'm geussing it's still apt based.
Those are in my opinion three key points where Maemo needs to be improved, as it is now on N8x0 devices.

The trouble is that apps don't run isolated from the OS. This makes things easier (as this is how stuff works on desktops, too) and more efficient (no middleware overheads), but at the same time exposes the OS to more unpredictable situations (bad packages will always be a problem), and the fact that the users get root is not helping in this regard either. As long as we don't have at least a chroot separated environment for apps, stability will always suffer.

No they don't of course. But Linux kernel has a nice way of dealing with apps that misbehave, using POSIX signals. This is enough on desktops, and should be enough for handhelds as well. Also, the device drivers need to be written in a way that a misbehaving app cannot crash the entire system.
The other thing is that apps should not be able to change system files. For instance, a while ago I had installed a vpn client on my N810, and tried connecting to work server just for fun, but it ended in changing the /etc/resolv.conf file, thus disabling any internet access. Imaging something like this happening to someone who's used to things just simply working!

One more thing that bothers me is that, when you install a lot of apps, system tends to become sluggish, and unresponsive, and quite slow. A restart helps, but after a while, it becomes slow again.

If its that simple, then I need to see that my entire MWS install can be reproduced on the tablet. If so, Maemo 5 just got really interesting.

Yes, I was thinking about it too.. and perhaps webpy would help.

Do yourself a favour and add one character :

http://www.web2py.com/

Same here; I pretty much agree with your compare, and find it complete.

What I like about Nokia E71 with S60 (SymbianOS 9.2) is that the default applications are solid and well integrated, and its compatible with the big evil world (example: Quick Office). An example which proves it isn't is the lack of OpenVPN support, and applications which assume a numerical keypad only for optimized usage. You can also install 3rd party applications many of which integrate well with simple configuration, but there is no such thing as a solid Application Manager. I also like the capability-based security of a microkernel-based OS such as S60, the fact it has J2ME, and that is has a large enough install base that corporations such as Google port their applications such as Google Maps to the OS. What they both don't have is good media management and usage like Apple products.