As stated, check the app manager, go to "Download", check the "All" category, and look for the "blue square" icon labled "Maemo5".

I think its been out for a while now, at least from a week ago. I did not get an alert the day everyone else did, but did get an alert previously. The Maemo update has been in my app mgr. for a while, but I closed the alert too fast as I was distracted w/something else, in the middle of shutting down. I chaled the update software up to something that dealt w/"flashing", so I left it alone.