Experience counters were mentioned as a new mechanic awhile back by Wizards of the Coast, and in this case, Kalemne benefits from creature spells costing 5 or more. For each experience counter, Kalemne gets +1/+1. The good thing about these experience counters is that they are much like emblems - they stay with you for the entire game.
While this isn't the best "Boros" (Red/White) Commander ever, she fits into pretty much any Red/White aggressive strategy ever. She's a good creature. Boros has plenty of 5 or higher CMC (Converted Mana Cost) creatures, such as Angels and Dragons. Another interesting thing to consider is that creatures that have an alternate casting cost that have an original CMC of 5 or higher will also trigger Kalemne’s ability. Evoke creatures in particular are a good option - as even though you have to sacrifice them immediately after cast using an Evoke cost, you would still get an enter the battlefield effect and the experience counter for Kalemne. The choices in Red and White include Faultgrinder, Glarewielder, Ingot Chewer, Reveillark, and Spitebellows.
Kalemne is a very efficient creature on both offense and defense. While most may prefer her as one of the 99 in a Commander deck, if you want a build-around “Voltron” style commander, Kalemne is a good choice.