I've been a happy user of both the original Nokia 770 tablet, the N810 and N900. From the point of view of a normal user I've been very happy with all of them, they have done what they promised and as a user I don't have that much to complain about. But..
As a developer I was drawn to the original tables as it was gobject/gtk+/gnome based with no bloat of C++ or some java stuff.
Made it easy to create software and somewhat easy to support both desktop and tablets in the same software, with some ifdeffing for maemo specific parts (gtk/hildon). That was more or less working in 2007-2008, but currently it's a blody mess.
Trying to support Gregale, Diablo, Fremantle and normal desktop gnome in the same app is these days such a pain that I've almost lost interest to do anything at all (one reason for Mapper developing at a snail pace currently).
Even Fremantle, that should use the latest technologies, (and Diablo) is stuck in the stone ages, gtk is in the 2.10 series (3-4 yeras old) Gregale is even worse with 2.6. Same with glib. Then we have gnome-vfs and gio mess.
And tablets specific Hildon changes, 3 almost compatible versions. Then we have 3-4 different UI styles to support.
And now upstream gtk+ is moving to version 3.0 and GNOME applications should move over to it. GConf is going to be deprecated with GSetting/dconf.
Now what the fuck are you supposed to do as developer wanting to support all tablets and desktop in the same app?