functions.php

<?php
//* Using the Gravity Forms editor, be sure to check "Allow field to be populated dynamically under Advanced Options
//* You will need to set the Field Parameter Name value to work with the filter as follows: gform_field_value_$parameter_name

//* Dynamically populate first name for logged in users
add_filter('gform_field_value_first_name', 'populate_first_name');
function populate_first_name($value){
	global $current_user;
	get_currentuserinfo();
	return $current_user->user_firstname;
}

//* Dynamically populate last name for logged in users
add_filter('gform_field_value_last_name', 'populate_last_name');
function populate_last_name($value){
	global $current_user;
	get_currentuserinfo();
	return $current_user->user_lastname;
}

//* Dynamically populate email for logged in users
add_filter('gform_field_value_email', 'populate_email');
function populate_email($value){
	global $current_user;
	get_currentuserinfo();
	return $current_user->user_email;
}

//* This method can also be used for custom user fields, e.g...

//* Dynamically populate phone for logged in users
add_filter('gform_field_value_phone', 'populate_phone');
function populate_phone($value){
	global $current_user;
	get_currentuserinfo();
	return $current_user->phone;
}