There are little quirks I've never liked about iPhoto. It seems slow to respond, it makes extra copies of files. At one point you could put iPhoto on a diet, but you shouldn't need to download software to unbloat other software. For purely online photo storage and minor editing, the photo features built into Google+ are quite good. I continue to maintain a Flickr account for photo sharing. For true desktop photo management, there are a couple of great options.
In terms of replacing iPhoto, look no further than Lyn to provide multiple viewing options and a rich set of features. Lyn includes histogram adjustments for color correction along with a set of non-destructive editing tools. You can view photos on a map in the application, to see where you took them. A number of upload options are available, including Facebook, Flickr, Dropbox, and Picasa (aka Google+). Lyn is also compatible with existing iPhoto, Aperture, and Lightroom libraries. Most common image formats, including RAW and JPG are supported. [Mac OS X $20.00]
Another interesting image manager is Pixa. It makes it easy to find and organize image files on your Mac, no matter where you choose to store them initially. An auto-tagging feature helps organize images by color and size, which is probably more useful for those of us who use images in a work context, but can also come in handy when you want to find specific images quickly. Pixa is integrated with Dropbox, so you can easily share images or simply make a backup that's stored in the cloud. [Mac OS X $30.00]