I've always felt that, in terms of gameplay, The Old Republic manages to strike a nice balance between encouraging socialising and allowing you to play solo. Sadly however, many UI functions that are supposed to support socialising are in a terrible state.
Let's take a simple example: the guild list. Every single time I log on, it's bugged when I look at it for the first time.
As you can see, the "show offline members" box is not ticked, yet every time I open the guild panel after logging in, what does it do? Show me a bunch of offline members. The sad thing is: this bug has been around virtually forever. I can't say for sure whether it's been there since launch or was introduced with one of the first patches, but either way it's been there for a long time. It's so bad that it's become second nature to me to mechanically tick and untick the "show offline members" box every time I open the guild window in order to fix the bugged display that I hardly even realise what I'm doing anymore. You could argue that it's not an important issue because it doesn't directly affect anyone's gameplay, but if players encounter the same bugs day after day, year after year, it doesn't exactly cast a great light on your game.
The worst offender however (in my opinion anyway) is the friends list. It's already gone through various stages of bugginess when the friends display on top of the screen wouldn't update correctly, and the "notes" field that's supposed to help you remember whose alt belongs to whom has been reset so many times that I've given up on trying to fill it in over and over again.
The biggest socialiser in my guild, who plays several hours a day and has friends in many different guilds, told me that when you're looking to fill those last couple of spots for your ops group, you might as well forget about your friends list - it's just that useless. I think that's saying something.
It doesn't even have a default sort that makes any sense: not alphabetical, not based on the last time the person was seen online, not based on when they were added - it's just a random jumble of names.
But the worst thing is that it's still entirely character-based in a game that encourages heavy alting. Even if you don't fill up the maximum of 22 character slots per server (for subscribers), there are eight different class stories you're supposed to play. Even if you only have five different characters and you want to be friends with someone who has the same amount, that still results in 25 friends list entries for each of you, just to keep in touch with one person. I almost despair these days when a friend tries the game for the first time or someone new applies to the guild. Will I remember to add them to all of my character's friends lists? The answer is probably no, and then they'll be looking for me when I'm on the one alt who doesn't have a friends list entry... Simply put, it's a logistical nightmare.
I'm not the first one to note this on the official forums, but understandably more people are busy clamouring for gameplay improvements and new content than for better UI functionality. Nonetheless I think that a little bit of time has to be made to implement quality of life improvements every now and then. A cleaned up, more practical way to stay in touch with my friends would definitely be my personal number one priority in that area.