In a stock application, there's really nothing wrong with an A4LD if you maintain it.
The only other bolt-up automatic option is a C4. The C4 doesn't have overdrive, but it's certainly proved itself as a durable transmission. Fi you do a lot of in town driving and/or track duty, the C4 is great because you never really miss the OD and can keep a decent gear out back. If you put alot of highway miles down, you're gonna want overdrive or you'll have to make up for it with a higher gear.
I read somewhere that there's some interchangeability between the A4LD and it's newer 5spd cousin. The newer
trans having better planetary gears and maybe a few other pieces. the bottom line was that there were things that could be done to an A4LD to make it better. Don't ask me what exactly, or who or where because I don't remember.