Hello LisaDarren,
I have owned my IS220D for a little over a year now, it's a 2006 model and I have indeed got the headgasket problem. I have to say Lexus in Poole so far have been good to us. My husband owns his own garage so, naturally, we were going to find workshop space and time to try and repair the car ourselves. When we telephoned Lexus to get the parts, they explained that this fault is covered under warranty if we wanted them to do it for us. So this morning, I have dropped off my Lexus to them and they will keep it for about 10 days and it should come back fixed. Being in the trade ourselves, I have to say we purchased our Lexus for the same reason you got yours. All I would say to you is please don't be disheartened. In the grand scheme of things, every manufacturer suffers faults at some point and it's how they rectify them that matters. Lexus have extended the warranty for this particular fault to 110k miles in order to try and get as many people sorted out as they can. I haven't had any other problems at all and I know plenty of other Lexus owners locally who bring theirs into our garage for servicing and MOT's and every one of those owners talks about the general reliability of this make of car.
I certainly think you could do a lot worse and certainly the Alfa's are not known for reliability! We see all sorts in our garage as we are an independent, therefore my recommendation would be to stick with it, once repaired I am sure you will be happy with it year after year.
Good luck.