The example (Talk:Location hack#Polling) you posted is far too complex and convoluted to use as a test case. I strongly suspect a side effect of the particular DOM manipulations you are doing to be the root of the problem.
A more appropriate test case might be e.g.:
In this case, I always see the alerts in the order I expect.
Nonetheless, I created Reading Content Globals to answer your query. This should be reliable, not to mention easier to read.
P.S. This isn't WikiPedia, and I don't like "chatting" on wiki pages. Please head to the mailing list (http://groups.google.com/group/greasemonkey-users) if you need further support. Arantius 15:50, 4 September 2010 (UTC)