Thanks so much for this article.
I recently got involved with Hadoop too. I also faced the RAM and 64-Bit CPU limitations on my laptop, so I decided to buy a new one :-D (finally I found a good reason for a brand new computer). I tried the Hortonworks Sandbox and I’m pretty happy with the experience and also with the learning material.
You forgot to mention HCATALOG, which is a metadata and table management system for Hadoop. It is very useful because provides a shared schema and data type mechanism, and a table abstraction, so the users need not be concerned with where or how their data is stored. Also Hcatalog interoperates with HIVE, PIG and other tools.