Yes, for the most part I would say it is very healthy. The number of questions and answers is growing. Participation seems to be good. And we are getting some high quality answers.
Mattdm plumbed aspects of this with his voter participation analysis where he showed that certain high reputation users could participate more in the voting process.
Instead, I took a look at voting in Meta. This is where the more concerned and involved members participate and contribute to the workings of the system.
Voting here reveals that this is a supportive community that welcomes positive contributions. This shows a good level of consensus and a positive attitude.
This is shown in the graph below of people with a reputation > 4000. The bottom axis shows the positivity-negativity index as a percentage where 0 means that the person cast an equal number of up votes and down votes. Data: 2011-04-28
Another indication of the health of the community is the time and effort that members put into improving questions and answers. See this query Top 50 Most Prolific Editors.
Here are our top five curators. Kudos to them for their stellar work on maintaining the high standard of this site. Data: 2011-03-21
Another way of looking at the health of the community is the Contribution Index. This is the ratio of Answers to Questions. On this measure our value of 3.6 answers per question places us second in the Stack Exchange family. This graph is from 2011-03-21
The graph below show the cumulative number of Questions + Answers since the inception of photo.SE. Though the cumulative number of Questions + Answers is growing the monthly volumes remain flat.
This is cause for major concern. For the first year at least, I would expect the site to show healthy growth and it is disturbing to see the site flat-line so early.
I suspect that this is because the exiting photo forums, such as DPReview are extremely popular and their members see little need to move to another forum.
In one month DPReview had 359,000 posts while our site has only 1,080 posts per month. DPReview completely and utterly dwarfs this site.
The huge number of members and posts gives DPReview a nearly unassailable advantage.
Data until 2011-03-21