Aside from the muscle atp aspect of creatine there's some interesting stuff about its role within the cns.system particularly at synaptic junctions...supplying atp, quickly and efficiently.. ..
(PDF) Functions and effects of creatine in the central nervous system
If you eat well, recover well arguably there is no need to supplement. I'm firmly in that camp in general.
It's worth exploring creatine though. I've tried it and noticed nothing before but I revisited it and think that it certainly helps with recovery from sprinting, especially max speed. Again, not exactly controlled experiments, it could for other reasons too but iis role in the cns may help perhaps in explaining why sometimes there seems to be little effect for some....perhaps the creatine pool iis never really depleted to notice, or there is plenty of it about and plenty of amino acids to make some if absent in the diet. Lots of variables there.
It's cheap, safe, well researched and more research reveals that it has many uses alongside cellular atp supply.
It could well be that extra energy is coming from an efficient cns too. So it makes sense that, as we know strength has a huge neural component, the more involved the cns is the more likely it is to drained....thus creatine aids recovery of the cns making it more efficient to boot.
I'm currently not taking any. I will when I start sprinting again.....5g with a glass of milk.
I'm not totally convinced but in general my recovery is better with it than without but only with sprinting.
Water retention? Yes but only with loading. But not always. Again could be due to other things......chasing a pump, creatine loading....is it creatine or glycogen ? Dunno.
Never noticed but I only do 5g.
It's said we use 2-3 g a day doing normal daily stuff.