Hate steam interface, has less features and in vista x64, I get more crashes with steam.exe and none with xfire64.exe...
I just miss launching games or browsing servers for all games from 1 window ( xfire in this case), I miss the FPS counter, I miss the in game screenshots ( yes I know most games have their own button, but it's easier to have it all in 1 without having to go to the options to change the key or browse 20 different screenshots folders... Also very easy 1 click uploader which uploads your pics to the xfire server, much faster than messing with imageshack or even skydrive... Also video recording and in game chatting in all games unlike with just a few non steam games and only steam games for the rest... For some older games like mohaa you have stats recording which is very nice. And I'm a stats whore I love seeing how much I've played a game and what games I've played, last time I checked steam forgets things older than 2 weeks...
I just like the app more than stuff like Fraps + imagehost + ingame options + steam + gamestats + playing stats, it's just so much in 1...
Yes those kinds of features are the only reason I keep hold on xfire. Steam chat is available across all games though, including VOIP, not just Steam games. Adding non steam games gives you the option to launch all your games under one program. Luckily xfire launches with games automatically (that is if it has decided to work, which it often doesn't want to do with me) so you can have both.
From a design point of view, Steam is much more proffetional. It is designed to work effortlessley. Nothing is of any hassle. I tried to use VOIP in xfire for the first time a few weeks ago, I heard it ringing so went into the UI and had no idea how to answer. The guy on the other end didn't know what I was supposed to do either.
Steam looks better too, subjective I know, but I have an eye for design. Nothign feels cluttered, colours and shading are minimal to avoid confusion. Steam has better friend managment, it's much easier to distinguish between different people and perform actions, like invite to group while in game for example. When I used to talk to people in xfire, if I had a couple of chats going it just wasn't very managable talking to numerous peope at once.
Xfire does have stats for a very select number of games, but Steam also has stats for all their latest releases.
Like you I still use Steam for its features that Steam lacks, like screenshots, but cannot stand using it for communication.
Personally I don't really have an option anyway, I have a horrible xfire bug where anything I type is also pressed in game. So in COD if I type a sentance with G in it, I will throw a grenade! If T is in my sentance I will start typing in game chat as well. Can't be bothered with it.