widget-favorite.php

<?php
/**
 * Favorite Widget
 *
 * @package      Core_Functionality
 * @since        1.0.0
 * @link         https://github.com/billerickson/Core-Functionality
 * @author       Bill Erickson <bill@billerickson.net>
 * @copyright    Copyright (c) 2011, Bill Erickson
 * @license      http://opensource.org/licenses/gpl-2.0.php GNU Public License
 */
class BE_Favorite_Widget extends WP_Widget {
	
    /**
     * Constructor
     *
     * @return void
     **/
	function BE_Favorite_Widget() {
		$widget_ops = array( 'classname' => 'widget_favorite', 'description' => 'Displays 8 random posts marked favorite' );
		$this->WP_Widget( 'favorite-widget', 'Favorite Images', $widget_ops );
	}

    /**
     * Outputs the HTML for this widget.
     *
     * @param array  An array of standard parameters for widgets in this theme 
     * @param array  An array of settings for this widget instance 
     * @return void Echoes it's output
     **/
	function widget( $args, $instance ) {
		extract( $args, EXTR_SKIP );
		echo $before_widget;
		
		$popular = wp_cache_get( 'be_popular_posts' );
		if( false === $popular ) {
			$popular = $this->load_popular_posts();
			$expire = 60 * 60 * 24; // Cache data for one day (86400 seconds)
			wp_cache_set( 'be_popular_posts', $popular, 'be_cache', $expire );
		}
		echo $popular;
		
		echo $after_widget;
	}
	
	/**
	 * Load Popular Posts
	 * @ return string, popular post output
	 */
	function load_popular_posts() {
		$loop_args = array(
			'posts_per_page' => 8,
			'orderby' => 'rand',
			'no_found_rows' => true,
			'update_post_term_cache' => false,
			'meta_query' => array(
				array(
					'key' => 'be_favorite_image',
					'value' => 'on',
				)
			)
		);
		$loop = new WP_Query( $loop_args );
		$output = '';
		if( $loop->have_posts() ):
			$output .= '<p>';
			while( $loop->have_posts() ): $loop->the_post(); global $post;
				$output .= '<a href="' . get_permalink( $post->ID ) . '">' . get_the_post_thumbnail( $post->ID, 'be_favorite' ) . '</a> ';
			endwhile; 
			$output .= '</p>';
		endif;
		wp_reset_postdata();
		
		return $output;
	}

}

function be_register_favorite_widget() {
	register_widget('BE_Favorite_Widget');
}
add_action( 'widgets_init', 'be_register_favorite_widget' );

So did you find out of this is an acceptable solution/work around for using rand?
I have a testimonials widget I'm putting into my core functionality and one of the options is rand, so I'm curious on what you ended up using :)

I never heard back from @nacin so I assume it's good. This is what I'm using on my project. Just make sure there's not too many of what you're querying (testimonials in your case).