Think of a classic P-bass pickup with a tad less highs and more low mid punch. Very pleasant woody tone. The tone sits extremely well and cuts through in the mix or with a band.
The sound became too mid/low-mid heavy when I used old half-round strings and old flats. I use D'addario XL nickel or DR nickel and stainless and the sound is great, I guess the bright strings are balancing out the low mid boost. For the archetypical Precision Bass sound I would look into the Fender 63' Pure Vintage which I also have. But for a great P sound with a slight twist, the SPB-4 is perfect. Steve Harris tones are of course easy to achieve (not like the man himself of course....!)
I had it on my bass for more than a year and I have no plans of replacing it, very happy with it. The price is right too.!