Octane stuff is kind of cool. This is the best article I found that describes what Octane does:
Octane Ratings
So octane needs depend on the compression of the engine. It looks like your bike has a fairly high Compression Ratio of 11.3:1
Total Motorcycle Website - 2005 Suzuki DL1000 V-Strom 1000
This would suggest that even though your bike has proven to run on lower Octane, as you pointed out, you will indeed see better performance with higher octane because your engine design (compression) is high enough to take advantage of a higher octane.
One thing to consider is the performance increase vs the cost increase. If the fuel economy increase is 5% but the cost of higher octane is 8% then maybe it's not as economical (of course better fuel economy is kinder to the planet and higher octane might perform better).