Depends what you do with it
As a dev (Business Intelligence), I use a snappy machine. There's nothing worse than running demanding applications on a machine that can't cope. At any time I might have SQL Server, SSIS, a dozen spreadsheets and word docs plus a couple of remote desktop connections and goodness knows how many peripheral apps running. My brain may feel like it's going to implode, but as long as my machine can cope then that's one less thing to worry about.
The directors on the other hand have nice light acer netbooks because they write reports, emails and use spreadsheets. So it comes down to what you use it for, but I won't need an upgrade any time soon.