If you haven't used wevtutil.exe to script event log tasks in Windows Vista or Windows Server 2008, you're missing out. The new tool makes getting events out of the log pretty easy, but the main thing is that it doesn't suffer from any of the drawbacks around getting field delimiting correct.
The tool's command to query events from a log is "qe", and takes a log name as a parameter.
If you want to specify a query expression, then you can use XPath with the /q switch. The easiest way to do this is to use Event Viewer to build a filter for just the events that you want, and then copy just the XPath expression out of the XML tab of the filter dialog in Event Viewer. Be careful to copy only the filter expression and not the XML that surrounds it.
Finally, the default output format of wevtutil is XML. However it dumps each event as XML, but does not include a root element- in other words it's not well-formed XML by default. To include a root element you need to include the /e switch and a root element name.
I put this all together in a batch file, with an example XPath filter that just gathers interactive logon events (event ID=4624, logon type=2). You can save this as a .cmd file and run it as an administrator on Vista or WS08 and it will pull up a list of your interactive logons in Internet Explorer (or your default XML handler application if you've changed the registration). It has to run as admin because it accesses the security event log.
If you're really good (better than me, which is not hard) you could write an XSL style sheet and put this into a report format.
REM (C) 2008 Microsoft Corporation
REM All Rights Reserved
if "%1" NEQ "" set outputfile=%1
REM The next command is all one line and has no carriage returns
REM The only spaces in the XPath are around the AND keywords
wevtutil qe Security /q:"*[System[Provider[@Name='Microsoft-Windows-Security-Auditing'] and Task=12544 and (EventID=4624)] and EventData[Data[@Name='LogonType']='2']]" /e:Events > %outputfile%