How does this differ from most phone OSs? WinMo has been doing it for years. Android has similar issues, where owners are at the mercy of the manufacturers if they are going to get updates.
Now, I bought my N900 with the full understanding that Harmanhattan/Meego might not come for it. I was fine with that, since the OS runs fine for me for the most part. As long as most major bugs are taken care of, I'm not too worried about my device. As you continue to use your N810, I expect I will continue to use my N900 for a while, particularly if capacitive screens are the future.
If Meego does come, I'll be happy. If it doesn't come, it is likely I'll still be happy, since I'm mostly happy with the phone as it stands now.