Most of your concerns are a moot point as beta tasks are a rare occurrence and highly sought after. It is rare that one will have such a catastrophic failure that there would be any noticeable effect on the host system. BOINC is specifically designed to be benign and invisible to all but those who are actively looking for it. Almost all errors or issues will simply end in the work unit terminating unexpectedly and the messages that it transmits to the administrators will be used to diagnose the problem(s). They frequently run a script during beta runs to award credit for work units that error out as well. There are very few potential downsides to opting into the beta program.

Thansk KWSN. I guess I am over reacting in cases like yours but Lawrence has summed up how I feel. I don't want to go around crashing my friends computers and some servers as that is just not cool.
By the sounds of it, there are no crashes etc due to Beta but it still sounds slightly riskier than normal. I guess I will have to decide once I have more experience.

At the very least, atleast I am still crunching on those computers which have no beta units assigned to them.