They're all alike in terms of external appearance. In most regards, the manual will be the same inside, too-- there hasn't been much changed on the bike, apart from the upgrades on the R-- but until someone has had a chance to examine both, no one can be entirely sure there's not some small but significant correction to a torque specification here, or a different bearing to be fitted there, or such, compared to the 2008 manual. I doubt that anyone here has been over both years' books with a fine tooth comb yet!
Bottom line, it comes down to how comfortable you are with the possibility of encountering some small change that wasn't documented in the older book. (And on eBay, who knows whether you're buying an original or a pirated copy, anyway, and whether it's even complete or readable?) From where I stand, if I were going to spring for the cost of a new bike this model year, the few extra dollars to be sure of getting the latest edition of the manual wouldn't seem unreasonable to me.
But be aware, Triumph doesn't necessarily issue a new manual annually... or even at the same time new models are introduced, though it's usually closely thereafter. I'd ask the dealer to check not only the part number but also the date of the current edition; then if it's different from the "08" books, I have him order one for me when I ordered the bike.
FWIW, the manual that was available this past spring is part number 3851760 issue 2, 2007.07. That's probably what most vendors will be calling an "08" manual because it covered the 2008 Street and Daytona 675s. If there is now an issue 3 available, dated during the summer or autumn of 2008, that would most likely be the one you'll want for a 2009 model.
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