I typically play AC on a laptop. I have a (very stable) iMac for photos, e-mail, music, etc., but since I can't play AC on it, I use my relatively older Dell Laptop. As of late, I've noticed performance dropping waaaaaaay down, so I bought some memory on the cheap, and went from 256MB of RAM to 1GB. Biiiig difference.
Now then, comes the question -- should I install Decal? I can only imagine how many majors I must miss out on, and while I only used Decal for about 9 months (tops) over the 7 years I've played AC, there has got to be some good apps out there.