I have also used Blueline Ballast for 6 years or so. Like Gary said, they run pretty cool compared to some other ballasts. They do not over drive the bulbs like some ballasts, so like Kent said, if you are looking to get as much par as you possibly can out of your light, then check Sanjay's and JBNY's threads for other ballasts.
I've had the blueline ballasts installed on many customers tanks, and never had a problem. The one blueline I've ever seen die was flooded with 100 gallons of SW, and it still worked for a few weeks before it died.
I do have a PFO HQI ballast overdriving a pair of single ended 20K 250 watt bulbs. It works good and burns the bulb a little whiter, but it sucks up a ton of power and kills the life of the bulb quicker.