I agree with sabujo, if you need a new burner I would buy the Sony DRU-500A.
I have them both (Sony DRU-500A and Pioneer A05) and the Sony is by far the most useful. I have not gotten mine to burn at 4X yet but it will burn + media at 2.4X and it will burn -R at 2 X (assuming the media is rated for that) so it is very useful. Not only that but I have not found any media that it rejects or cannot use. The A05 on the other hand will burn Ritek 4X media at 4X but that is the ONLY media I have gotten to work with it! I have made tons of coasters trying to use media that the Sony readily accepts.
I assume they will eventually fix these problem but unitl they do there are a lot more happy Sony users then there are Pioneer users.
Good luck with whichever one you get..........