I started out with an Eclipse 12gal (alongside a 55gal which was my first tank) and know others that have. I bought mine for only $50 on sale, and at this price, I still wouldn't recommend it as a nano. There are a lot of things that are not ideal for the reef setting, including the lighting and filtration system. I spent extra just to retrofit power compacts in, and it worked for keeping a pair of harlequins for some time (see gallery). Again, there are better solutions for nanos for your money, including some that the others mentioned for just over $100... these are specially fitted so that they are reef ready... the Eclipses are not the best nano reef systems (because of the lighting & biowheel issues mentioned.
As I think has been mentioned already in this thread, nanos are not ideal systems for beginners to start with, go bigger if you want more water stability. This is not to say it can't be done; there are success stories and you can go to nano-reef and the nano forum here to read about them and get suggestions. However, larger systems may seem more hassle to start up; but you will find they are much less of a pain to manage in the long run.