Re: What's the point?
I suggest you check out the xda forum subsection for your device, but a few of the benefits are:
Init d support
Choice of kernel
Performance options (choice of governor/scheduler, over clock, under volt, memory usage, amount of memory available for apps to use - my galaxy w now has 390mb available up from the stock 350mb )
More frequent updates then your manufacturer offers
Newer versions of Android than your phone will officially get
A myriad of customisation options not offered by any stock ROM