Here's what the StoredProc which grabs all of the users with the custom properties I want looks like.

SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO

CREATE PROCEDURE [dbo].[Custom_UserProfiles_SelectAll]
/*
Last Modified:		2011-11-27
*/

@SiteID  int

AS

CREATE TABLE #usersWithProperties
(
SiteID int,
UserID int,
UserGuid uniqueidentifier,
FirstName nVarChar(Max),
LastName nVarChar(Max),
Email nVarChar(Max),
Gender nVarChar(1),
Supervisor nVarChar(Max),
SupervisorID int,
JobTitle nVarChar(Max),
Organization nVarChar(Max),
MobilePhone nVarChar(Max),
WorkPhone nVarChar(Max),
Photo nVarChar(Max),
Birthdate nVarChar(Max)
)

INSERT INTO #usersWithProperties (SiteID, UserID, UserGuid, FirstName, LastName, Email, Photo, Gender)
SELECT SiteID, UserID, UserGuid, FirstName, LastName, Email, AvatarUrl, Gender
FROM mp_Users
WHERE SiteID = @SiteID
AND mp_Users.DisplayInMemberList = 'True'

UPDATE #usersWithProperties
SET	Supervisor = (
		SELECT u.Name FROM mp_Users u
		WHERE u.UserID = (
			SELECT uP.PropertyValueString FROM mp_UserProperties uP
			WHERE uP.PropertyName = 'Supervisor'
			AND #usersWithProperties.UserGuid  = uP.UserGuid
		)
	)
	,SupervisorID = (
		SELECT uP.PropertyValueString FROM mp_UserProperties uP
		WHERE uP.PropertyName = 'Supervisor'
		AND #usersWithProperties.UserGuid  = uP.UserGuid
	)
	,Organization = (
		SELECT REPLACE(r.DisplayName, 'org_', '') FROM mp_Roles r
		WHERE r.RoleID = (
			SELECT uP.PropertyValueString FROM mp_UserProperties uP
			WHERE uP.PropertyName = 'Organization'
			AND #usersWithProperties.UserGuid  = uP.UserGuid
		)
	)
	,JobTitle = (
		SELECT PropertyValueString FROM mp_UserProperties uP
		WHERE uP.PropertyName = 'JobTitle'
		AND #usersWithProperties.UserGuid = uP.UserGuid
	)
	,MobilePhone = (
		SELECT PropertyValueString FROM mp_UserProperties uP
		WHERE uP.PropertyName = 'MobilePhone'
		AND #usersWithProperties.UserGuid = uP.UserGuid
	)
	,WorkPhone = (
		SELECT PropertyValueString FROM mp_UserProperties uP
		WHERE uP.PropertyName = 'WorkPhone'
		AND #usersWithProperties.UserGuid = uP.UserGuid
	)
	,Birthdate = (
		SELECT PropertyValueString FROM mp_UserProperties uP
		WHERE uP.PropertyName = 'Birthdate'
		AND #usersWithProperties.UserGuid = uP.UserGuid
	)
SELECT * FROM #usersWithProperties
DROP TABLE #usersWithProperties

We had a lot of other fields but this should get you started.