Grant Foster has written another post about data analysis in his Open Mind blog. This time he analyzes visual Cepheid data and compares it with published photometric data. His conclusion:
Yes, Virginia, visual data really can compete with professional photometry. But to do so requires large quantities of data. Experience and skill on the part of the observer doesn’t hurt either! It’s a lot of effort to accumulate nearly 5,000 visual observations of just one star (and Wayne Lowder observed a lot more than just this one star!), but its scientific value is tremendous. The value of the data set taken as a whole is comparable to that from professionals.
Amateur astronomy, whether by high-tech or just by eye, is a rewarding task, both for the observer and the analyst.
Here is a light curve he made of data from Wayne Lowder, a famous AAVSO visual observer, compared with published professional data:

Click here to read the blog which goes into much more detail, [1] but is quite accessible for new observers too. Grant's writing is really good at being entertaining and useful to many different skill levels.
Links:
[1] http://tamino.wordpress.com/2012/06/06/seeing-the-light/
[2] http://www.aavso.org/forums/variable-star-observing/visual-observing