I like my DT225 from the ebay blowout, but it has some limits. Every affordable trackball seems crippled to some sense. I desire four real buttons, so the DT225 in PS/2 dies, and a wheel, which several of the cheap Kensingtons lack. I also strongly like a left-handed-friendly layout, so the Logitechs are out. Do I need a $125 Kensington or CST to be happy?