Hot on the heels of a major API update, Foursquare announced Monday that it has updated its iPhone app and site with two new features: photos and comments.

Users can now comment on each other’s check-ins, which seems like pretty obvious functionality. It’s a nice reminder that Foursquare is still just a startup, iterating like crazy to meet user demand for features they expect. The new commenting system will likely serve a wide variety of uses, but could most importantly become the primary way for Foursquare users to meet up when in the same location. As long as users have push notifications enabled, one could quickly ask to meet up with a friend who just checked in nearby. Comments work from the mobile app, on the website, and from check-in links posted to Facebook or Twitter.

Another feature for supplementing check-ins, Foursquare now lets users upload photos with their tips. Now you don’t have to just trust the user, you can see for yourself.

Finally, here’s something that Facebook can’t even get right: a history page. At foursquare.com/history, users can now see a perfectly preserved archive of all the places they’ve been, with photos and comments included.

All of these features are now available on the app for iPhone, already live in the App Store. Android is slated to get the updates later this week, while webOS and BlackBerry users will have to wait for January. Other platforms, including Nokia, will brought up to speed in early 2011.

One commenter seemed particularly thrilled about the mention of webOS in this most recent announcement from Foursquare.

"Thanks for including the WebOS in this - we're usually the left-outs who have to just watch while the others play!"

True enough, which proves that a smart startup knows it can’t really afford to snub its users on any platform. Most of the comments, in general, seemed really positive about the changes.