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In my opinion, no. iOS 8 is a huge update but most of the awesome stuff (widgets, app integration) require the apps to be updated which they aren't right now and won't be for months to come. The straight up user features are minor IMO and most if not all can be found as Cydia tweaks. Remember that running iOS 8 will also break a lot of App Store apps.
 
When comparing stock iOS to jailbroken iOS, I don't think there is no advantage.. Given the openness of a jailbroken iOS.
 
Yes, you can show off a beta to your friends, but you can also show off a jb to your friends :p

I prefer the jb than a buggy initial beta.
 
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