nice thing about PR 1.0 is that a lot of the extensions are part of the actual build.

definites for me everytime are:
Mouse Gestures by Optimoz Team
gmail notifier 0.4
sage: RSS reader
cute menus: adds pictures to your shortcut menus, looks cool
adblock: block adverts, block frames, block shockwave ads (right click = done). Want to block every image from ads.yahoo.com? just block ads.yahoo.com/*

Weather extension is also available but not public yet.

Themes? The default I thought was awesome so i used it for a long time. I just goto the themes web page and sort by most popular or by most downloads and DL away. I used Qute for a long time too... You might not see all the themes yet, since 1.0 is so new a lot of things haven't gotten updated.