There is a lot of information about the UNO32 and the MAX32 at the chipkit forums (http://www.chipkit.org
). The MPIDE for the chipkit boards also supports other common PIC32 boards like the CUI32 or UBW32. There are pre-compiled boot loaders available for these as well. The CUI32 and UBW33 are boards that do not use the FTDI USB chip but instead make use of the on-board native USB connectivity of the PIC32MX795 and PIC32MX440 chips.
So the MPIDE environment is quite versatile when it comes to support for PIC32 hardware.
I started using the UNO32 as I am much more familiar with PIC hardware then Atmel. Used to do assembler on 8-bit PIC's. I also have a variety of programmers for PIC, whereas I had nothing "modern" for Atmel. Having lots of parts laying around I did eventually buy a couple bare PCB for Duemilanove. To get the boot loader into the chip I picket up an AVR ISP MKII. I guess my thinking is that with the Arduino IDE in particular, and programing in C on AVR or PIC32 the differences between these platforms are no longer all that significant.
For some shields and libraries it is much simpler to use the official Arduino hardware. I.e. I am working with a GSM shield from Seeed Studio. It turns out that out of the box the Seeed Studio GSM module is wired to use digital pins 7 and 8 for software serial. Well, the software serial library is not supported on the chipKit hardware, it hasn't been ported yet. The workaround is to use the second hardware serial port. But that required some hardware hacking to bring the 2nd serial port pins from the UNO32 to the appropriate place on the GSM shield. Not a huge deal, but certainly required a few hours of time to get it sorted out. Anyways, don't get me wrong, I like the chipkit hardware, it is really nicely done and I am certainly going to be working with it for some upcoming projects I have in mind.