Karl,
I am in exactly the same position as you. I am leaning more toward the Optoma because it has a 3 year warrenty (swap-out, not RTB) as well as a 3 year zero dead-pixel warranty (again, swap-out). I have not seen an H57 but am willing to "buy blind" based on seeing the H56A -- it was very impressive for DVDs, which is why I want a PJ.
The HS50 looks like an awesome machine on paper and is potentially more "future-proof" because it is high def. That said, it is effectively new technology (auto iris system, etc.) so it is probably a riskier proposition -- its warranty is only 1 year which perhaps reflects this. Who knows, it could be durable and last a decade but for nearly £2K I want some safety. This forum is riddled with stories of people having problems with LCDs after having had them only a couple years (before I get flamed, yes, I know, people have also had great success with them).
So, at the end of the day be patient and see them both if you can. But remember, there is more to the story than specs. Unless you have loadsamoney I think it is best to look at these as investments and move carefully.
Best,
John