[UPDATE AT END OF POST]
OK, I have upgraded my test blog site to WordPress 2.5, to see if any problems occur with my current plugins etc., before committing myself to upgrading my 19 other blogs.
It would appear that a couple of things may be of interest to others…
1) Using the WordPress Automatic Upgrade plugin, the process bombed out at the ‘cleanup stage’. To clarify, the upgrade proceeded as normal, but the procedure halted when the process attempted to delete its temporary files. I was able to continue (WordPress had me login in again), click on the Manage link, go to Automatic Upgrade, and finish off the process successfully (AFAI can tell). Go here for the general plugin page, and here for the latest update info.
2) The Sticky Post plugin (previously found at http://blog.vishalon.net/Post/88.aspx, though that page is now removed or perhaps the permalink structure over there changed?), that enables you to keep a specific post on the front page for as long as you want, without constantly fiddling the time stamp, appears to be temporarily broken by WordPress 2.5 . I suspect this was due to code changes within WordPress that deal with handling which posts should be displayed. If you have the plug in installed, upgrade to WordPress 2.5, and find that none of your posts appear, along with an error of WordPress database error: [Table 'wp_posts' from one of the SELECTs cannot be used in global ORDER clause] at the top of your page, login as normal, and deactivate the Sticky Post plugin.
( SELECT SQL_CALC_FOUND_ROWS wp_posts.*, 2 AS N FROM wp_posts WHERE 1=1 AND wp_posts.post_type = 'post' AND (wp_posts.post_status = 'publish' OR wp_posts.post_status = 'private') ) UNION ALL ( SELECT wp_posts.*, 1 AS N FROM wp_posts INNER JOIN wp_postmeta ON wp_posts.ID = wp_postmeta.post_id WHERE wp_posts.post_status = 'publish' AND wp_posts.post_type = 'post' AND wp_postmeta.meta_key = 'STICKY' AND wp_postmeta.meta_value = '1' ORDER BY wp_posts.post_date_gmt DESC LIMIT 1) ORDER BY N, wp_posts.post_date DESC LIMIT 0,10
I still want to carry out further testing before upgrading my other blogs, but I’m reasonably happy, so far at least.
For further info on the final release of WordPress 2.5, see here, here, here, here, here, here and here.
[UPDATE]
See this post for further details on plugin compatibility testing with WordPress 2.5