What firmware should I use for my 3500? Thanks!
For best results, please describe exactly what you want to use your 3500 to do. (i.e. burning which type and brand of media, etc.)
Me, I have always used the stock firmware and never regretted it.
You can also look at the NEC firmwares overview. Using any firmware aside from the official ones will void your warranty!
See my sig. If you are using any of those media, the firmware is 2.18. For the record, all teh firmware I went through up to 2.18 did a equally outstanding job. See here for a concise summary of what is available:
If you willing to do it at your own risk then I recommend any of 3500 modded f/w by Liggy, Dee-27 or Quick. They all provide good performance, increase in ripping speed and raise your burning speed noticeably.