I've had no problems with it. The only other programmer I have is a 15 years old PICStart+ so I can't say how the PK3 compares to anything really - but it works. When developing I tend to use a bootloader though so the PK3 doesn't get used that much.

One thing I've read about the PK2 is that Microchip won't add support for new chiås as they come out but recently I read somewhere that you could download new definitition files for it so.... Also there supposed to be some sort of basic logic/protocol analyzer application for use with the PK2 which I don't think is available for the PK3.

So again, the PK3 works fine for me, YMMV.