Thanks for your reply Lexo.
The concern of replacement batteries is a real one and not an 'if'', as I plan to keep the car for quite a while and don't see myself upgrading any time soon-ish. And, No, I didn't realise the warranty is 8years/160 on the batteries. However, does that also apply to '06 and '07 models, or is that something relatively new? Appologies for all the questions, but I'm quite new to the whole Lexus world ;)