Do I need to upgrade to 5.x-2.0-alpha4 before going to D6?

We hope that this is no longer necessary.
I tried an upgrade from 5--1 to 6 on a test site last month and it all worked.

However:
1. Try on a test copy of your data first!
2. There are issues with there being multiple copies of image data in the database, which causes the upgrade to fail because of index uniqueness being required. There is an issue open for this (if not several). I've no idea how this multiple data gets created in the first place, and we need someone who's good with SQL to come up with a way of reliably cleaning it up prior to import. We also could use samples of it -- if you find you have this problem, please report back!

The multiple data issue it #583076: Error on Database Updates for 6100 when upgrading to Beta3: 'duplicate entry' for primary key.

I just upgraded from 5.x-1.0 last night to current (d6) and it worked beautifully. Couldn't have asked for better.

Thanks for letting us know!

Closing this issue now.