Performance aside, here is what I hate about Skype compared to MSN / WLM: privacy.
(1) Skype logs you in to your last known status / on MSN you could choose before login (for example, "appear offline"/"invisible"). If I just want to check if a contact is online without my aunt start chatting, I can't.
(2) There is no easy way to block whole contact groups temporarily. When I'm at work, I don't want my friends to see me online; when I'm at home, I don't want to be contacted by co-workers.
(3) Say I'm chatting with Bob, and he goes offline just before I send him a last IM. This IM will be delivered the next time that we are both online. Even if one of us is "appearing offline"/"invisible". So we have a way of knowing when someone is hiding: just send someone a message when they are offline. Bah.
(4) Not related, but the delivery of old messages is awful across platforms.
What annoys me the most about these bugs (1-3) is that they seem so easy to fix, and yet nothing is done. Meh. Do you have similar frustrations?
Skype doesn't make it easy to use two accounts. There is no "multiple accounts" feature where you can be logged in as one or both; instead, you have to log out and log back in again as the other. Sometimes, you might be on-call, so chatting with friends is OK, but you still need to be available to coworkers.
The problem with Skype is that it's totally closed. I use a multi-protocol IM client, with multiple accounts, so I can chat with people over AIM, FB, Google Chat, my work chat, and so on. Sadly, despite the fact that my work has Google Apps, which includes chat, they have standardized on Skype instead, so I need to have an entirely separate client, and log out and log back in when switching between work and personal accounts.
