Pluck seems to be a fine flat file PHP content management system. I had trouble installing it last year, but gave it another try last week, and it installed without any trouble.
The control panel is very nice - both clean and logical. And it's fast. Pluck is designed as a CMS, but comes with a blog module built in, along with a gallery module. You can create a number of blogs and galleries with just a few clicks each. The script also includes a statistics area, but the stats are limited to just two - total site "hits" (actually, page views) and browser type (IE, Firefox, etc.). If you want more stats, just add the code for Google Analytics to the footer.
Installing a new theme is easy - just download a zip file of the theme you desire, and then use the Pluck control panel to install it. Just click "Install new theme" and use the dialog window to find the zip file. Then activate the new theme by using a pull-down menu. A couple dozen themes are available at the Pluck website, but unfortunately, most of them are quite similar. But I found a couple that I could live with. Fortunately, it is very easy to create your own theme for Pluck, since each theme consists only of two files - an index file and a css file. Since virtually everything is defined in the stylesheet (layout, columns, etc), the index file is extremely simple.
Pluck is also fairly search engine friendly. For each page you create, you can fill in blanks for META keywords and description. Page urls, however, do include a question mark, so they aren't perfectly search engine optimized. In my experience, this doesn't make a great difference to most search engines.
You can include an e-mail box in any page on a Pluck site to allow visitors to send you a message. Like the rest of the Pluck script, this is coded very cleanly and looks very nice in the various themes I tried.
Compared to other open source flat file content management systems, I rank Pluck quite high. It meets most of my personal criteria: fast, easy to install, no dependencies except PHP, logical control panel. The built-in blog engine and gallery creator add value, as does the e-mail form.