My upgrade of EAGLE from 4.x to 5.3 arrived from CadSoft this morning. Installation was straightforward. Looks like it's going to behave itself.
I haven't started exploring the new features yet (what with there being real work to do today). On a quick look, though, it's nice... and the bundled library collection has expanded quite a bit since version 4.1 (though a lot of them are user-contributed and contain only a few parts; a bit of central work on compiling master libraries would have been a good idea).
Update: the user interface is improved in various little ways (though I'm not sure I like the new delicate pastel look). It has PDF export built in! And cross-reference labels (though the mechanism is a bit awkward). And... user-defined attributes! Yippee! That's a feature I'd really been missing. I'll have to investigate just how this works in detail, but it should certainly allow me to tag passives with things like tolerance, voltage or power rating, dielectric type, and so on... normally leaving these blank, but having them available when I really need to differentiate things in the BOM.
The autorouter seems (based on a couple of quick tests) to work about the same as ever, and still doesn't deal nicely with user-defined power/ground fill (polygons may fall apart at the last minute), and still likes to route traces through the corners of SMD pads (I don't know that this is an actual problem, but it doesn't look right). It seems to me that the overall result looks a bit cleaner than the old version's usual output.
I still need to try running some of my indispensible ULPs (slightly adapted from user-group programs) to make sure they still work... and then see how to incorporate the new attributes into the BOM program.