I installed SS3 beta2 with blog module. And there may be some bugs to prevent from working with SS3 beta2, as I write below.

1. Table name of comment
Comments module uses comment table instead of pagecomment table. So we should change table name from pagecomment to comment in BlogManagementWidget.php.

2. getCMSFields of BlogEntry.php

Fields(such as Author, Date) are not shown in admin page. To fix this, as far as I saw BlogHolder.php, the tab name should be changed to Main.Root.
In addition, editor is also not shown. I don't know why this works, but I commented out $this->extend('updateCMSFields', $fields), editor appeared.
After these changes, the getCMSFields would become below.

	function getCMSFields() {
		Requirements::javascript('blog/javascript/bbcodehelp.js');
		Requirements::themedCSS('bbcodehelp');
		
		$firstName = Member::currentUser() ? Member::currentUser()->FirstName : '';
		$codeparser = new BBCodeParser();
		
		SiteTree::disableCMSFieldsExtensions();
		$fields = parent::getCMSFields();
		SiteTree::enableCMSFieldsExtensions();
		
		if(!self::$allow_wysiwyg_editing) {
			$fields->removeFieldFromTab("Root.Main","Content");
			$fields->addFieldToTab("Root.Main", new TextareaField("Content", _t("BlogEntry.CN", "Content"), 20));
		}
		
		$fields->addFieldToTab("Root.Main", $dateField = new DatetimeField("Date", _t("BlogEntry.DT", "Date")),"Content");
		$dateField->getDateField()->setConfig('showcalendar', true);
		$dateField->getTimeField()->setConfig('showdropdown', true);
		$fields->addFieldToTab("Root.Main", new TextField("Author", _t("BlogEntry.AU", "Author"), $firstName),"Content");
		
		if(!self::$allow_wysiwyg_editing) {
			$fields->addFieldToTab("Root.Main", new LiteralField("BBCodeHelper", "<div id='BBCode' class='field'>" .
							"<a  id=\"BBCodeHint\" target='new'>" . _t("BlogEntry.BBH", "BBCode help") . "</a>" .
							"<div id='BBTagsHolder' style='display:none;'>".$codeparser->useable_tagsHTML()."</div></div>"));
		}
				
		$fields->addFieldToTab("Root.Main", new TextField("Tags", _t("BlogEntry.TS", "Tags (comma sep.)")),"Content");
		
		// $this->extend('updateCMSFields', $fields);
		
		return $fields;
	}

I also wrote step by step instruction of installing SS3 with blog module on my blog. ( http://gsoc2012ss.yaunix.com/blog/how-to-install-ss3-beta2-with-blog-module/ )
I am newbie to SS3, and there may be some misunderstandings and wrong directions.

Thanks in advance.

Regards,
Yuki