Need explanations about roms

[uudza]

Hi,I`m new here.
I read pretty much posts,but i still don`t get it-what`s the point on changing roms?
Will it make the pda go faster?(I eman if I don`t change to wm6 or so)
I got:
ROM version:2.17.7.2 WWE
Radio version:02.07.10
So what could be the best thing to do,so I get maximum what i can from my device?
AND-if i install wm6 or something like that-how would change the spped of my 9100?

[lmd0990]

Why not , but be careful not brick it

[uudza]

But do these touch,wm6 and so on,makes the device really slower or just a bit?

[lmd0990]

I realy not exprienced that

[uudza]

And with what should i satart if I want a custom rom?
like http://forum.xda-developers.com/showthread.php?t=367375
or wich is better?
And in wich can I do the most with my fingers?like these touch themes?