Hi,
IMHO all the computer makers have a bad habit of having "entry level" machines whose specifications will cause them to be borderline useless.
However, to their credit Apple seems to be rectifying this in that none of the machines on their website are that badly underpowered (although the Power PC machines will feel sluggish compared to the Intel ones they still re not underpowered). That said, I do think that all makers could benefit by putting a simple chart in their "buy" section with popular software programs listed along with the total machine RAM needed to run the software over the normal OS image.