I see no benefit to any other coins, they are all just other devs trying to get in on the action.
Casascius already touched on this subject way earlier in the thread, but I'll reiterate what I think is the same idea: It's not necessarily about benefit to the userbase, in the sense I think you mean.
Today, there was a lot of hoopla about Amazon supposedly adopting Bitcoin. Now, that's not likely to be true at all, but let's assume Amazon or some other big player really did think the idea was good. Would they just go and start accepting Bitcoin, as is? Maybe. It seems just as likely to me, however, that they would just create their own equivalent, maybe with some alterations. There's plenty of talk about what works and doesn't work currently already here, from the perspective of the current crowd of enthusiasts. A big retailer might well have ideas of their own about that. So, it's far from given that Bitcoin is what they'd go with, and any currency they might create would get huge exposure simply by virtue of being proposed by a big company. That doesn't necessarily mean Bitcoin would just die off, but it could set severe limits on the growth potential.
Personally, I think the big guys are still very interested in creating more centralized internet currencies, like Facebook credits etc, since that allows them more control. Personally, I think that's not going to fly, we've seen centralized internet currencies before and they haven't worked out very well, but that doesn't mean it won't be tried again. I think we're going to see more experimentation with centralized currencies before serious consideration is given to decentralized ones. If that does come to pass, then the question is what kind of features do big retailers want in a decentralized currency, and those may be very different from what Bitcoin offers. Anonymity isn't likely to be of interest to them, or for the mainstream userbase, either, for example.
IMO a big player taking interest in Bitcoin right now might not be such a good thing for Bitcoin. The whole system is still very small. The bigger the userbase gets, the better the chances of Bitcoin being the currency of choice for everyone are, but push it too early and you might just see a fork backed by one or more of the big players gain traction instead.