I might be missing something, but I am getting several javadoc regression test failures on windows with tip:
    changeset: 780:8ec3a824f925
    tag: tip
    user: jjg
    date: Fri Dec 10 07:38:28 2010 -0800
    summary: 6504896: TreeMaker.Literal(Object) does not support Booleans

I believe they pass with b120:
    changeset: 746:1dd813a529cf
    tag: jdk7-b120
    user: mcimadamore
    date: Mon Nov 15 14:41:21 2010 +0000
    summary: 6999635: Multicatch: crash while compiling simple code with a multicatch parameter

At least the one test I tried passes. Note that you have to run the tests from b120 as well as the jdk from b120 - the tests have changed.

Here are the failures:

com/sun/javadoc/AccessH1/AccessH1.java
com/sun/javadoc/AccessSkipNav/AccessSkipNav.java
com/sun/javadoc/JavascriptWinTitle/JavascriptWinTitle.java
com/sun/javadoc/testClassCrossReferences/TestClassCrossReferences.java
com/sun/javadoc/testClassTree/TestClassTree.java
com/sun/javadoc/testConstructorIndent/TestConstructorIndent.java
com/sun/javadoc/testDeprecatedDocs/TestDeprecatedDocs.java
com/sun/javadoc/testExternalOverridenMethod/TestExternalOverridenMethod.java
com/sun/javadoc/testHeadings/TestHeadings.java
com/sun/javadoc/testHref/TestHref.java
com/sun/javadoc/testHtmlTableTags/TestHtmlTableTags.java
com/sun/javadoc/testIndex/TestIndex.java
com/sun/javadoc/testInterface/TestInterface.java
com/sun/javadoc/testJavascript/TestJavascript.java
com/sun/javadoc/testLinkOption/TestLinkOption.java
com/sun/javadoc/testLinkTaglet/TestLinkTaglet.java
com/sun/javadoc/testMemberInheritence/TestMemberInheritence.java
com/sun/javadoc/testMemberSummary/TestMemberSummary.java
com/sun/javadoc/testNavagation/TestNavagation.java
com/sun/javadoc/testNewLanguageFeatures/TestNewLanguageFeatures.java
com/sun/javadoc/testOverridenMethods/TestOverridenPrivateMethods.java
com/sun/javadoc/testOverridenMethods/TestOverridenPrivateMethodsWithPackageFlag.java
com/sun/javadoc/testOverridenMethods/TestOverridenPrivateMethodsWithPrivateFlag.java
com/sun/javadoc/testPrivateClasses/TestPrivateClasses.java
com/sun/javadoc/testStylesheet/TestStylesheet.java
com/sun/javadoc/testTypeParams/TestTypeParameters.java
com/sun/javadoc/ValidHtml/ValidHtml.java


This test
   test/com/sun/javadoc/AccessH1/AccessH1.java

gets this failure
Sub-test 1 for bug 4636667 (AccessH1) FAILED
when searching for
.header h1.title {
    font-size
    text-align
    margin
}

I looked at a few of the other failures and they were similar.