I'm currently trying the pdaXrom out, but I must admit I miss Opie - much faster and has all the apps I want (whereas pdaXrom has undefinied symbols errors at the mo and not much in the feed). No doubt these failings will be fixed in the fullness of time.
OZ can also use GPE as its GUI - this is X11 with Matchbox much like pdaXrom, and it remains compatible with OZ packages and has a more up to date libc. There was a link for an early release on the forum (try a search for GPE if you're interested), but it is very much work in progress.
Take a look at openembedded.org (and at the mailing lists) if you're interested in progress etc.
Si