Glad this got bumped up. I wanted to update my experience. As noted above, I purchased a jar of Arid Extra Dry Cream for use on a one-month ride through the US and Canada in July.
I chose the cream because unlike gels or sticks which melt and become unusable, not to mention the potential mess, the cream comes in a container which is basically air tight so if it melts, it's still usable and it won't leave a mess.
The cream did, in fact, melt a few times. I know I opened it once or twice in mid-day to see a pool of liquid in the container. I simply screwed the lid back on tight and put it back in my pack. Every morning or after any shower, though, the cream was perfectly usable. I was impressed.
After returning home to Memphis in late July, I continued to use and carry the Arid cream on my bike. After numerous melting and solidifying cycles, the cream separated into a liquid and solid and hasn't returned to a state of being a cream.
So... the cream did work, but in excessively hot conditions, the life of the deodorant cream appears to be limited. Fortunately, it's not too expensive and easily replaceable.