Many people erroneously think the value of bitcoin comes primarily from its "features."  In my opinion, a large part of its value comes from the fact that it has been endlessly beaten-up since 2009 and remained resilient--bitcoin has in fact grown by leaps and bounds in spite the world's efforts to thwart it.

Side-chains are technically brilliant.  If there was a way to implement them without any changes to bitcoin they would have my support.  My concern is that the desire to facilitate experimentation of features with questionable utility may not outweigh the very real technical risk of implementing them and the potential loss of confidence that may result.  I will be able to make up my mind more definitively after I have studied the to-be-released side-chain white-paper.  

That being said, I think things will unfold exactly as they need to.  Spin-offs can become a reality very soon, where side-chains will take longer.  But the new awareness that both are possible helps take a hammer to pump-and-dump alt-coin schemes.  By the time side-chains ever have a chance to become reality, the perception that they are needed may have already waned.