I started with arduino, and I had no microcontroller experience. The community, examples from the absolute ground up, and vendor (sparkfun, adafruit, etc) support is excellent. It all makes for a really enjoyable experience. Digikey and mouser get you parts fast. Ebay and random asian websites get you parts slow but cheap. If you want graphics (eg. TV, or monitor) though, best go with the pi. A pi costs less than an arduino graphics shield. Ethernet is doable at least.
Totally agree, Sparkfun and Adafruit are certainly Hobby friendly, I am still tempted to do some AVR work as they had a great tut on Sparkfun... Which reminds me of another reason I decided to dip my toes with the Launchpad - I do have a Pi and its GPIO voltage is the same as the MSP, so they seam to be a good fit. I haven't actually interfaced them quite yet, so I could still end up releasing the magic blue smoke.
There is also an arduino style IDE for it. http://energia.nu/
I did attempt to get this going but failed miserably - something to do with a Java binding that wasn't linked properly. I have zero Arduino experience so though I might as well go 'native' anyway
You cannot have a science without measurement. -- R. W. Hamming