Your typical spoilboard cutter probably won't work very well with acrylic. You'll most likely get a lot of melting.
I think for acrylic, your best bet would be a 1/2" upcut spiral, probably a single flute "O" flute.
The tool you linked to will be great for MDF, though.IF you want something cheaper, just find a large 2 flute straight bit, or something like this.
http://www.amazon.com/Magnate-Surface-Planning-Bottom-Cleaning/dp/B0006B0QXO/ref=sr_1_1?s=power-hand-tools&ie=UTF8&qid=1335699447&sr=1-1]Amazon.com: Magnate 2707 Surface Planning ( Bottom Cleaning ) Router Bits - 2-3/4" Cutting Diameter: Power & Hand Tools