I don't suppose anyone tried deploying with PostGreSQL & JRuby? I keep hearing how JRuby simplifies deployment issues as well as other problems such as connection pooling. If MySQL clusters find joins distasteful, maybe PostGreSQL could do a better job?
Not JRuby, but I've done a postgres app, but it's small. Very small. So small it doesn't matter 
Also, for the record, my understanding is that mysql cluster can *do* the joins, it just doesn't do them very fast all the time. particular outer joins.
It *won't* do (at least 5.0.34) queries like:
select ... WHERE col1 LIKE '..' OR col2 LIKE '..'
You have to split those into two queries and union them.
And some other little oddities like not being able to update more than 32000 rows at once, etc.
There's a gotchas/limitations document on their site. Just be sure to give it a really good read.
