From a decoding point of view I'm not sure it would offer much advantage over more common run-of-the-mill off the shelf, and much much cheaper consumer/hobby scanners and receivers.
Why not?
Because P25 decoding is a straightforward software (or ASIC) implemented procedure - in fact you can download P25 software patches for encoding/decoding off the internet for free. There is no secret to it, hence just about any scanner with digital function and processing can have P25 intergrated.
The exception to the above of course is where P25 has been implemented using a manufacturer or brand specific IP core for specific or custom application, or has had encryption added - in which case no scanner with general P25 functionality would be able to monitor.
Where your Johnson 5100 may well offer advantage is in rf performance i.e. the ability to receive and demodulate a P25 transmission in the first place, only because the cost would suggest the quality of the components in 5100 are probably of a higher quality than run of mill components in off-the-shelf scanners. But I say that with reservation, because products like the 5100 tend to be aimed at a specific market and have a whole bunch of design features for that market e.g. packaging durability, operational temp range, water resistance and so on, which cost money to implement and have little to nothing to do with overall rf performance.
Last but not least, the 5100 is very limited as a scanner both in terms of bandwdith and overall frequency coverage - its designed for P25 usage and not much else.
I suspect one or other of the good Radio Shack type scanners would be better value, at half the price or less, and would offer you as good P25 performance with a bunch of other general scanning functions the 5100 wouldn't give you.
..... thats my personal take on this product.
