performance:
It's strange it's running slow for you. My 867Mhz 12" is actually very snappy, but you may be right about the RAM... I started out at 640MB (so more than yours to start with) - I've now got 1.12GB and find it really speedy compared to a similar spec WinXP Pro machine
heat:
yup, seems to be fairly common with PowerBooks... they got hot !
I'd suggest grabbing a copy of Temperature Monitor:
http://macupdate.com/info.php/id/12381 to keep an eye on it !
I use a Targus ChillPad (a couple of USB powered fans) but there are other 'lap' solutions, and things like the iCurve to raise it off the desk to improve airflow
must-have apps:
these are very much personal recommendation but for me;
<ol>
<li>AdiumX Instant Messenger (MSN, Yahoo, Jabber etc)
<li>QuickSilver application switcher
<li>skEdit HTML/source editor (
www.skti.org)
<li>TimeLog (for client billing)
<li>Skype VOIP communications
<li>BluePhoneElite for managing SMSes and calls
<li>e2sync (if you use Entourage it adds iSync functionality)
<li>OnyX for system maintenance
<li>iScrobbler (for AudioScrobbler updates)
<li>Meteorologist to keep track of the weather
<li>Virtue for multiple desktop support
<li>SizzlingKeys (for iTunes) - iTunes control at your finger tips
<li>SafariNoTimeout - when 60 seconds just isn't long enough to open that web page, nothing else will do
<li>StartupSound - you don't hear it often, but sometimes it's enough to wake the dead !
</ul>
... just have a search for any of these on macupdate.com for the latest versions
expect to see a lot more suggestions added to this list !