Can I use Sim-IM to connect my GoogleTalk account?
Yes, you can.
To connect to Google Talk jabber server, use the following settings:
[x] Use SSL
[x] Use plain text login
[x]Manually specify jabber host:
Why ICQ User details do not work properly on systems with utf-8 locale?
Sim-IM detects you language, by the name of you system's encoding. (Strange idea, isn't it?) When you are using utf-8 encoding, language can't be guessed, because utf-8 is for all languages. So you should manually set encoding that should be used for getting ICQ userinfo. This can be done at Setup/User Info/Encoding. (Changing encoding here would effect ICQ). Russian users should choose CP-1251 encoding, German users should choose ISO 8859-15.
Can't see my friend's online status in ICQ, thought he is online for sure.
First of all check that you've authorized him and he has authorized you. Then check that your firend is not in "Not in list" group. According to recent AOL changes being in "Not in list" group is the same as being not authorized. Just move your friend's contact from this group and it would be visible to you.