Be the first to 
- ICQ is an efficient tool for instant messaging
- Lets you connect with both ICQ and AIM network users, supports SMS, voice and video chat
- ICQ allows you to play games and send greeting cards easily
- ICQ lacks filters, history search and advanced per-contact customization
- You cannot talk to MSN Messenger or Yahoo! Messenger users with ICQ
- ICQ does not support encrypted communication
- ICQ lets you send instant messages and files to ICQ and AIM users.
- You can also send SMS messages to mobile phones/devices and receive replies in ICQ.
- Equipped with microphone and webcam, you can voice and video chat with ICQ.
- Push2Talk lets you talk instantly with ICQ 5 contacts walkie-talky style.
- ICQ can keep messaging histories per user.
- Lets you apply ICQ spam filtering for non-buddy messages and hide from or ignore certain users.
- Integrated white pages search makes it easy to find like-minded people on the ICQ network.
- ICQ Xtraz let you send animated greeting cards or play games together.
- You can set your own display photo or choose from a gallery of ready-made pictures.
- ICQ supports Windows 9x/ME/NT/2000/3/XP.
Feature-wise, ICQ is part reminiscent of the good old days, part exploring more than just text messaging. The essential functionality has been present then and is in ICQ today: great white pages, text messaging and a history (which could be searchable). But ICQ also forays into (and quite nicely integrates) audio and video conferencing as well as SMS messaging. With other ICQ 5 users, you can even use Push2Talk, a walkie-talkie mode of chatting.
Unfortunately, ICQ does not support encrypted communication. It's also a pity that ICQ doesn't support group chats and offers no per-contact customization of alerts, sounds and the like. The ignore, invisible and visible lists are useful, though, and there's some spam control, too. Filtering on the user level might still be better, however.
Trying to be slim and easy on the surface, ICQ offers advanced features as "Xtraz", which also include greeting cards, images and games you can send, set and play. As a client from AOL, ICQ unfortunately lacks MSN/Yahoo!/Jabber connectivity.
