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Kinda new to this stuff, curious why more guys don't use the Propeller chip?
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From what I can tell, it seems less approachable.

And what about interrupts?

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No interrupts, but you have eight processors (cogs) running simultaneously. 32K RAM. I got a kit from Parallax for $99 to learn it.
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Yeah, it's my understanding that you can have one of the eight, or perhaps more, waiting to read inputs while the others run the rest of the program (programs?).

I'm trying to read 14 channels from an RX using interrupts on the Mega 2560, storing the values, and "relaying" them to output servo signals, or to activate different functions of the program, so I don't think the Propeller would work well for my main intended use.

That aside, the Propeller does have a lot to offer, in many ways more than the Arduinos. Generally speaking, I think the main reasons Arduinos are so widely used are that they're easier to use since there's less to set up with them and they tend to initially be more of a complete solution for hobbyists. It's pretty easy to get started with them and use them. If people stay with it, I can see them easily "graduating" to other microcontrollers that might be more capable for some uses.

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I'm on vacation this week, but have been reading the books. The good thing I've found is that Parallax puts their books online for free.
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Each Cog has two independent timers that you can set to time the pulses. I haven't been able to play with this yet, but I plan on doing something similar, reading pulses from a receiver.
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Ah, OK. Let me (us?) know how it goes. Some more people might want to give it a try then, if it works well for this kind of application.

I think the two downsides of the prop are a lack of ADC's and the learning curve for passing values between cogs; it takes a bit of learning to figure things out but its not impossible by any means. For simpler tasks, the arduino is far easier to use.

As far as reading RC channels is concerned, if your channels are always produced in a sequential manner, the prop should be able to measure them on a single cog. If they are being produced in a random order, that becomes more difficult, i wasnt able to read the pins fast enough using spin to get accurate pulse width values.

Im a complete amateur with these things, my microcontroller experience is comprised entirely of three motion control hobby projects, one using an hc6811 and assembly, the next a propeller using spin, and the last is an arduino using wiring. So take this all with a grain of salt.