You still will get good returns (usually), just lesser than what you would get with 1 BTC. I also added another 0.1 BTC to the bankroll last night. Here are my profits from my (somewhat) small investments:
If you have some spare BTC, and are willing to risk losing some of your investment, then I would go for it.
Worth because it's better than letting your money on a wallet without generating any interest. Surely the profit won't be big, but it's not so low like lending money on Poloniex and this kind of thing... Sometimes you will earn more or less, depends the house luck also. I personally think it's a good idea.
Profit won't be big? It has returned almost 9% in under 3 month! Even lending money on Poloniex has been averaging about 6% interest a year. That is equal to or better than anything found in the real world.
Poloniex lending is almost 100% risk free though, bankroll investing is not.