Looking under the hood of Android, they seem to have thrown away 5-10 years of Linux development (not the kernel, but above it). Innovation in some areas, but steps backwards in others. I suspect they stripped down and (badly) rewrote so many things to be able to target lower end hardware, but hardware has advanced quickly in the last year. That decision may come back to bite them, if they can't rewrite their way out of it fast enough.

Are there any advantages to this "balance" of half-closed stuff, compared with a mostly-open system?
I can't see any advantage to having more closed things, but I'm genuinely interested in why you do.

The ability to tinker doesn't have to mean *you* tinker :-) It means others have more ability to make interesting apps and improvements (even in the main interfaces) for you to download and use.

I can see advantages in using Google's *apps* because they are good at some things, but those advantages will spread to other platforms too, partly from Google wanting to spread to other platforms like Maemo, and partly from other people writing good apps too now that the platform is available (as a phone). I'm sure I'll use some Google apps on my N900.

The N900 is the very first Maemo phone and looks a lot more advanced than the first Android phone did, which is a great sign for Maemo's future over the next year - if they can capture the imagination of good developers. It is likely to improve in the same way that Android has improved, but it is built on better technology underneath, hence my comment about Google's design may come back to bite them.