1) After I create a new Blog entry or Panel, I get a page that says "This document already exists". But the new document is created without any other problem.

I cannot reproduce this, neither on the default XWiki installation, neither on www.xwiki.org . Are you sure you are not trying to create a document that really exists? Please check again with another document name.

2) In the WYSIWYG editor, if I highlight a word and include a leading space (ie " word") and then format as bold, the result will be "* word*" instead of bold text. It works fine if there is no leading text.

Yes, this is correct. The syntax for bold markup has changed a bit, requiring that no empty space exists between the starting asterisk and the first text character. I think our WYSIWYG team forgot to implement this change in the visual editor. Thanks for noticing this, it will be fixed in the next beta version.

3) I am sure I am not the only one running multiple wiki deployments (e.g. /xwiki09 and /xwiki10). 1.0b1 allows me to use a web path other than /xwiki and it will still display, but all links are directed at /xwiki.

You have to make a small chang for this to work: locate WEB-INF/web.xml and change <display-name>xwiki</display-name> to match your desired application name.

Also, when mixing xwiki versions you should take care that each version uses its own database, since the new version might modify the database in an backwards-incompatible way (although we take extra care regarding backwards-compatibility).

4) There is a problem with viewing attachment revisions. I attached logo.gif to XWiki.XWikiPreferences twice. Then I clicked "1.2" to look at the history (/xwiki/bin/viewattachrev/XWiki/XWikiPreferences/logo.gif). I got a bunch of unformatted menu text that looks like leftovers from 0.9. I've pasted the page text below.