. Is it ok for most of the non-banking (read: non-critical) applications to leave the Sql Server Isolation level to the default (Read committee)?

I think you mean 'read committed' ;)

Answer...it depends on the requirements. Just because it's non-banking (so to speak) doesn't mean it isn't critical.

Since you're using SQL 2005, have you looked at the new snapshot isolation level? Granted, it won't be used every time, but in instances where you need the 'best' of read committed and read uncommitted, it can help.

Kevin