Ultratherms are great, in fact they are some of the best available. As with all UTH's they must be regulated by a thermostat, and monitored with a probed thermometer.
Here are some good thermostats, stay away from the junk sold in pet stores:
Budget: http://www.amazon.com/Hydrofarm-MTPR.../dp/B000NZZG3S
Mid-range: http://www.reptilebasics.com/thermos...stat-prewired/
Best: http://www.spyderrobotics.com/home/products.html
And here is a good probed thermometer: http://www.walmart.com/ip/Acu-Rite-I...ndingMethod=rr
While I'm at it here are 2 threads I suggest you read through:
BP care: http://ball-pythons.net/forums/showt...ius)-Caresheet
BP cage setup (step by step): http://ball-pythons.net/forums/showt...With-Pictures!
On a side note what UTH's were you looking at? Most are relatively inexpensive ($15-$30)