Is slow charging a Lithium Polymer battery any better for it?
The battery university does tend to suggest that, in genereal, lower charge rates lend to longer battery life.

However, it is also well known, as even pointed out in the comment by Ignacio Vazquez-Abrahms, charging the lithium ion to a lower voltage and therefore a lower capacity, helps to extend the battery's life.

Every lithium charger that I have seem charges on the CC-CV algorithm and terminates charge when the current in the CV stage gets to 1/10 the current of the CC stage.  So if you start with a very low charge current, the charger won't terminate charge until the current is 1/10 of that small current.  The result will be a very full battery!  A very full battery may not have as long a life as described above!

I.E. if you charge your battery at 1000mA, it stops charging at 100ma.  If you charge it at 100ma, it will continue charging until the battery is only accepting 10mA and very full.

Also,  I don't have the paper now, but when I purchased a LiMn2O4 battery from a Nissan Leaf to rebuid for a different project, they gave me their research paper on charge/discharge of the battery.  They found a faster charge rate of 15000 mA was better for battery life than slower or faster charge rates.