Just a few things I like about PICAXE microcontrollers:
PICAXE BASIC - The PICAXE implementation of BASIC is highly intuitive and very robust. It is easy to code a wide variety of functions from flashing LEDs and reading simple analog sensors, to more advanced tasks like driving servos and interfacing with external eeproms.
Programming Editor - Like the language itself, the Programming Editor strikes a nice balance between user friendliness and functionality. It features automatic color coding and rudimentary syntax checking. It also has a decent simulator, debugging features, and a serial terminal.
Documentation - The PICAXE manuals and datasheets are comprehensive and coherent. The language features and controller capabilities are clearly explained and well documented. I've always been particularly impressed with PICAXE Manual 3 which covers hardware interfacing.
Scalability - The PICAXE line includes 8, 14, 18, 20, 28, and 40 pin variants making it easy to pick the right axe for the job at hand. For those who want a jumpstart on building projects, RevEd also offers a line of compatible project boards.
Continuous Improvement - RevEd continues to produce new PICAXE offerings to take advantage of developments in microcontroller technology and other related trends. As just one example, the most recently released chips feature support for capacitive touch interfaces.
The PICAXE Forum - The PICAXE Forum is a fantastic resource. If you have a question about PICAXE, the odds are great that the question has already been asked - and answered - at the forum. The forum is closely monitored by a team of spirited volunteer moderators as well as RevEd staff who frequently weigh-in when technical questions about PICAXE arise.