Reduces weight very slightly, reduces lost horsepower very slightly (engine has to turn less components, with less drag) reduces engine spin up lag very slightly so improves responsiveness (for same reason) and increases oil pressure to the rest of the components in the engine very slightly.
On the converse, will increase engine vibration, drive shunt when going on/off throttle and also possibly noise - yep, you guessed it, all very slightly...
I don't know what the measured differences in all of those are, but very slight.
On it's own (this is as an un-informed deduction just from basic principles, so please don't take this as trying to dampen down sales from cebul's valued bringing of group buys to the forum) I doubt very much that it's worth doing, but as part of doing lots of other mods to the engine, it would be?
No doubt some luders that have done this will be able to confirm (likely

)/deny (unlikely

)/put some specific numbers to what I've said above
