I've been using xCoins for nearly a month now and I've cashed out profit. It's a pretty good system - you can fully automate your "lending" (read: selling) with minimal effort for around 15% ROI on all BTC passed through the system.
Charge-backs are indeed an issue and can wipe out your profits. However, as mentioned above, xCoins have recently introduced a scheme where they automatically cover all losses due to charge-backs/fraud until you are back to at least 50% profit. This can be considered insurance, designed to cover any early stage lenders who are unlucky enough to hit get with a charge-back early on, prior to making much profit. xCoins say most people who have been using the system for a while are in profit anyway as the CB rate is relatively low.
Other risks include PayPal closing your account due to "high risk" activities. This risk is decreasing with time, I think, as PP now has relationships with Coinbase etc. now and seem to be softening their stance on BTC. Still, it's recommended to start lending in low volumes, and slowly increase it so as not to raise flags/alarms. Also, don't withdraw big sums from PP immediately - always leave enough $ in the PP account to cover possible CBs - this will goes some way to re-assuring PP.
I know that it is a top priority of xCoins to find another payment processor that is more BTC friendly and doesn't allow CBs (or at least provides decent seller protection), but in the meantime 15% ROI on all BTC that you sell via xCoins is likely worth the risks.
Finally... counter-party risk. As always, don't store lots coins on the exchange. Transfer a small amount of BTC and start lending. Replenish balance when empty.
TLDR:
xCoins seems legit, and there's potential for an easy profit - but start with small volumes, assess the risk/reward ratio, read the forums and decide for yourself.
Oh, and use the following promotion code when joining up for up to 25% discount off all commission fees: jbh184
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