Canon 30D vs 400d

I am interested to know a couple of things about the differences between the 400D and 30D from an underwater use perspective:

1) How valuable is the increased size of the viewfinder (and pentaprism vs pentamirror) on the 30D compared to the 400D?

2) How valuable is spot metering on the 30D (I've used it before on land, I'm just trying to come up with specific underwater examples)?

3) Is it worth the difference in price now that the $100 to $200 rebate is out for the 30D (still $100-200 more than the 400D)?

4) Lastly and not really a comparison question, aside from a Canon EF-S 60mm macro (which I'm pretty convinced on), does any one have a suggestion on a more general purpose lens (like a 17-40mm f/4L USM lens)?

Thank you

I upgrade from the 300D to the 5D and the viewfinder improvement was hugh on land, but in the housing it was not that much. I expect this to change when Aquatica finally ships their upgraded viewfinder.

Spot metering is no big deal at all underwater. It's very unlikely that a small bright spot is the limiting factor in your background exposure.

I think that the 5D is a massive upgrade from the 300D, and despite the extra money is an amazing camera and a very senible way to go. The 400D seems less justifiable.

DPReview posted a 400D review over the weekend - that would be worth a read:

http://www.dpreview.com/reviews/canoneos400d/page29.asp

Alex