I do have a live experience with running several (from 2 up to 30!) strategies simultaneously. See e.g. here:
http://forexsb.com/forum/post/30120/#p30120
From here I can write about existing strengths and weaknesses.
The examples from my previous post should mainly stress my opinion that the automation of creating the Strategy Portfolio would be much helpful in finding a really well diversified and robust trading system.
If you have a look at the last example before the end of the article, I bet that the majority of traders would never trade any of the 3 individual strategies. But still, if put together, they were able to create an agreeable equity of the whole portfolio. Now imagine that for example the 1st ugly equity represents a trendfollowing system, the 2nd ugly one a breakout (or false-breakout) system and the 3rd ugly one a system for choppy markets with lower volatility. Like in real markets - no individual strategy brings profits all the time; every strategy has its strong and weak periods. But when you put them together you can achieve a perfectly diversified and robust overall strategy.
Now back to FSB. Most of the time I have used the Generator for searching new profitable strategies. I run it many times, with different settings. Thus I obtain hundreds of individual strategies. In order to be able to work with them in a more detail later, I need to strongly reduce their number first. You can imagine that I only keep strategies with "nice" reasonable equities; the rest of strategies with "ugly" equities are thrown away.
Theoretically this proces has sense = if you take several nice strategies and make a well diversified portfolio by puting them together, you should obtain a robust winning overall system. Unfortunately, my experience says that this is valid only in backtests, but not necessarily also in live trading.
Therefore I now tend to combine strategies generated by FSB with "nice" equities with clearly defined hand-made strategies that often show rather "ugly" equities, to create a more robust overall trading strategy. Here I would see the big advantage of the automated creation of Strategy Portfolio - a human brain and restricted time for work cannot compete with powerful computer processors.