The only problem with this is that "beats per minutes" depends on what beat you're talking about. If you want to group things with similar tempos, you could create comments like "fast" "slow" "walking tempo" "really fast", etc. With a BPM analyzer, you may not get an accurate representation of the tempo, especially if you have music with irregular meter, or very ethereal stuff, or anything that lacks drums or percussive instruments. For example, running a bpm analyzer on the first movement of Shostokovich's 6th symphony would probably not yield accurate results.
In short, if you're willing to go to the trouble of manually entering the BPM's anyway, you might as well just make your own custom tempo distincitions.