The new Steripen Ultra has many similarities to my extensively tested Steripen Adventurer Opti reviewed HERE, and without long-term testing of this new addition to the Steripen line, I'll simply compare them both.
BENEFIT: Ultra is a 32 grams heavier (just over an ounce), and treats the same number of liters per battery life. I like that it is USB rechargeable. Fits the mouth of a regular Gatorade/Powerade bottle, and has a count-down timer plus a "smile or frown" visual aid that lets you know if the water has been treated or not.
Ultra uses miniUSB rechargeable lithium batteries, thus it can be recharged in the field with a backup battery, or a solar charger. This eliminates the need to carry additional batteries.
COMPROMISE: It weighs more than the Adventurer Opti
I will continue to use this unit over the summer and update my experience once I have more time on trail with this unit.
Seen below is the comparison for the Opti and the Ultra (screenshot from steripen.com)
The Ultra uses a user friendly and simplistic "Smile or Frown" approach to knowing if the water has been appropriately treated.