My current version just supports titles and tags (I use the tags for the image alt attribute, and both the title and tags together for the title attribute, hopefully to help with SEO).
Adding descriptions/rating/comments gets a little tricker if you want them to show up on the album view page. If you want to change the image link to go to image.php, then you can have all that stuff there no problem. Getting it to work on the album page will require some fancier JavaScript/AJAX work -- but since I'm not planning on using comments/ratings/etc. myself, it's low priority.
Slideshow is something I am interested in adding. I don't think it's going to be too hard, I just need to figure out what sort of controls it needs and where to stick them. I'm going to try to have that for an upcoming version.
Slideshow is not very hard to add. It's designed generic as a dark to black grey page with basically just the image to fit for all. Since slideshow is a plugin, you'll have to use the nightly for this. Just install the plugin and copy slideshow.php from any of the default themes to your theme. All you have to do then is to add thte slideshow link to your page (works from album and image pages).
See our already updated functions guide or the plugin file itself for more info about options.
I've updated my live site with a slideshow now -- it's based on timer code that plugs into jQuery.
in album.php look for this line:
image.css('display','none').fadeIn(200);
and change number (it's the milliseconds to take to fade in) to a higher value for for a slower fade -- I set mine fast to keep things snappy :)
At least, that's the way it works in FireFox. IE seems more abrupt, not sure if a longer values gives you a better fade with it.