I am totally enamored with Flickr, the social photo sharing service. It has plenty of nifty features; but more than anything it's just super simple to use. I love looking through the (ever changing) latest photos, as well as sharing a few of my own. Flickr is exactly the solution I needed to provide to my mom for her to share her photos. My sister has also found it to be a great service.
The WordPress Flickr plugin is a fantastic effort, and really blends the best of two great products. This is what I set up for my mom, so that she can share her photos from her blog without requiring her or her readers (ie: our family) to juggle bookmarks to different places. I suspect I'll put the plugin to use for my sister, as well.
I value Flickr's (extreme!) convenience, and I enjoy the groups functionality, but I just can't reconcile paying someone else to host my photographs when I have my own server and plenty of bandwidth. The flip side of this is that I've yet to find a photo gallery package that I can host myself that provides me with all the features and convenience that I really want. I've been eyeing gallery for what feels like forever, but I'm just not sold on it. I've been using jigl for quite some time, and I'm reasonably happy with it, but it's a little brittle. Providing titles and descriptions to my photos is a little more time consuming with jigl.
I've looked at all the other WordPress photo gallery integration efforts, but none have really struck my fancy. Carina has been using the Exhibit plugin, and she seems happy enough with that. I forget why I didn't like that one, now, but there was some reason. Probably something vague, just like my aversion to the python programming language.