Is Parallax Propeller a good product?
It does what it does very well. Spin is a nice easy language to get your head around and as an interpreted language, quite efficient with a nice compact bytecode. 

Spin is not blazingly fast, but raw PASM is pretty sprightly (50ns instruction cycle).

Having 8 identical cores with a completely deterministic instruction cycle makes for a very versatile little chip. As long as you remember it is a microcontroller and play within its limits, it's an incredibly nice chip to use.

I keep a stack of proto-boards handy for rapid prototypes. The ability to do crash and burn compile/test cycles in a matter of seconds (it takes about 7 seconds to download the absolute largest program into the chip and huge compiles rarely take more than 2 seconds - more often in the hundreds of milliseconds) makes for a very fast turnaround development cycle.

Parallax really concentrates on the beginner market, so along with being a pretty potent little machine, it is very easy for a greenhorn to get working in short order.

Native 32 bit integer math is nice too.

 I did not mean that to sound like Parallax products are only suitable for the beginner. The Propeller is a "grown ups" processor with plenty of oomph in the right places, it's just that Parallax provides a lot of hand holding for the beginner to help them get started.