For reading ebooks you've got FBreader or any of the palm readers (I believe most of them work)

For playing media, media players abound I would suggest Canola2.

For Mobile internet access, the built-in browser is pretty good, one of the best I've seen on a mobile device. It can crash however, and does sometimes, although not nearly as often as IE7.

And then the Garnet VM works decently enough. It's rapidly getting better

All of the above do NOT require any sort of tinkering or command-line interface, and (normally) you shouldn't even know that you're using linux. They all install nicely through the App Manager (either through built-in repositories or from their respective websites) and all have very nice GUI interfaces (Much better than most palm software)

GPS can get slightly more complicated, although MaemoMapper is an EXCELLENT piece of software that for normal GPS and mapping usage works beautifully.

You should be warned however, that the GPS doesn't usually get a fix very quickly, although I've found it to be really good at keeping fixes. It depends on where you are and how clear a view of the sky the device has. For example, driving home today, I couldn't get a fix from the woods where I was camping, but I got one while driving on the freeway home. It's not something I would want to rely on, but it's not terrible or anything.

Overall, the device is very reliable and the only times it's crashed on me are when I'm experimenting or pushing the envelope in some way (installing rotation kernels etc.)

I absolutely LOVE my N810, but for me the draw is the open nature of the device and the little hacks and tricks you can use to enhance your user experience. Basically the device can be whatever you want it to be (within the confines of a pocketable box of course) which is the big pull for me.

So, I think the N810 would probably work for you, if your uses are pretty limited to what you've listed there. If you want to do anything advanced though, it does require rolling up your sleeves and doing some reading. This forum is a great resource for that, as well as the Maemo Wiki.

My apologies, I seem to have gotten carried away :P

So, in a nutshell:

Yes, the N810 works (very) well for what you've listed, but if you really need ease-of-use and reliability, the iTouch might be a better solution. It all depends on how computer literate you are and how much you're willing to learn to make the device into exactly what you want it to be.