I prefer to use legacy with the following:
Palm Blazer v4.3, on Palm OS.
Mozilla 1.4.3 on Suse 9.0
With Mozilla, having cleared the cache, even the new, non-legacy mode actually works pretty well (even though I posted elsewhere that it did not - I had not thought to try clearing the cache before reading here). The board is offset, covering some random text, but perfectly usable, and analyse board works well enough.
On the Palm, the new board code does not work at all - I get a blank board with the from and to squares highlighted. Even with legacy, it is not possible to make a move on the Palm - pieces get highlighted and moved, but tapping the "move" key does not seem to transmit the move to the site, as the move is not made. It was not possible to make a move on the Palm, even before the recent board updates.
A small legacy board now fits entirely on the screen on the Palm, which is an improvement.