The SD630 is brand new and here's a link to a DP review page (not a review)....
http://www.dpreview.com/news/0602/06022109canonsd600.asp#specs or http://www.dpreview.com/news/0602/06022109canonsd600.asp#specs
And it looks formidible... 6MP, 2.5" LCD screen, ISO 80~800, 30FPS VGA, a 9 point AiAF and a 4x optical zoom. The price seems cheap too at $400-350. With a spec sheet and price like that the unsuspecting might not ever consider a DSLR!?? I have a SD400 which is similar with 5mp, ISO 50-400 and a 2" LCD (currently $199-299). You can' beat these pocket digicams for convenience - but in practice I carry my 10D and Lowpro AW75 everywhere 97% of the time. I usually carry 3 lenses plus a flash half the time. And in practice the most use the SD400 gets is as a substitute for a camcorder! Yeah - we actually view MPEG video more than our miniDV video footage!
And at $50-100 of difference I would spring for the SD630 if I were in the market for a pocket camera. However, I might encourage you to save your cash for a HD video camera. The SD630 and the SD400 are not very compelling substitutes for your Rebel or any DSLR. And the SD cameras are not going to have any advantage (except size and convenience) over the DSLR. Speed, power (usable ISO 1600), image purity, RAW and reaction time are always going to be considerably better with the DSLR... and after carrying the SD400 around I sort of reverted into only using the DSLR. I used to have a rebel until - as you feared... I got it wet walking through the surf on a cruise while carrying two toddlers in my arms. I had to replace the shutter to get it working again - then I sold it to be free of legacy issues (I disclosed the shutter replacement and failure issues in the listing ~ it still got good money - mayb e because of my feedback or the extensive description and multitude of photos I posted). Then I decided that I had spent a huge sum on digicam equipment and went to a used 10D on ebay for a scant $100 more than what I sold the rebel for. Yeah... the 10D is just like a D-rebel in a black magnesium body - but I did it because the 10D debuted for $2200 and I could get it for $600! So that was MY WAY of sidestepping the depreciating residual values. Oddly enough I got 75% of the cost of my D-rebel (since I kept the kit lense) and got the 10D for 72% off!
My 10D is such a dream to handle in rendering images. I have a tough time stepping down to a pocket camera. Plus - the pocket SD gets beat to #@*! So I recommend that if you get one to immediately get an LCD screen protector for it. And if you can resist - save your dollars for a HD video camera for when they drop under $1000. They seem to get about $1500 and shoot 70 minutes on a miniDV tape. THAT is something to justify your HDTV - since the HDTV programming is so marginal IMHO.
Aside from that - - may I enquire which lenses you have for the rebel? It might not be a bad idea to add a couple of sharp lenses to your kit instead of an SD630 - as the KIT lense is sort of OK - and there are a few mucky lenses out there - it could be you don't have the sharpest lenses on your DSLR - and a sharp lense can make your images POP - plus the "rig" will handle a little better with a focal range you enjoy.
Sorry to be deflecting your thinking a little - it's just my 20-20 rear view mirror thinking. You kno... if I could do it again - then I'd be one step closer to the HD camcorder ---- and one step closer to a HD DVD player which was just released last month! I saw one the other day and
Best Buy and it's only $499... and the movies are about $25-30 each. Gotta have THAT!
Oh yeah... half my
Disney cruise images were shot with the still alive D-rebel ... and the 2nd half were shot with the back up SD400 after the D-rebel died from surf exposure. There's another reason to have a backup. If you still need a backup - why not a $50 G-1?
http://www.dpreview.com/reviews/canong1/ I bought my 1st G1 for aboiut $750 5 years ago ... and I paid $400 for a 1G micordrive. These things depreciate so quickly - it makes me think twice about buying high tech when it's brand new... excpet for HD DVD players and HD camcorders. Those things I covet (in a nice way, of course!). Oh yeah... upsode of a D-rebel and a G1 are that they share the same batteries and memory - and the rebel is at the bottom rung of resale cost so they can be had for next to nothing. It does half VGA at 30FPS and shoots 3MP with the same external flash as the D-rebel! It is about 4x as bulky but it is smaller than a d-rebel and probably able to be 1/5th the size of the DSLR kit. Or at least it is 1/5th my DSLR KIT.
Oh yeah... 2% of the time I carry the SD400 and 1% of the time I carry the G1. And I am almost as happy to use the G1 because it takes slightly nicer images than the SD... it's the larger sensor - and the fact the specs are not ov erly ambitious compared to the the SD.
Those super slim SD digicams come with tiny 1/2.5" sensors and more pixels while the G1 has the larger 1/1.8" sensor with fewer pixels. It makes for larger sensor sites and cleaner images.... DIGIC 2 can only correct so much.
My G1 images ocassionally POP while the SD400 images NEVER pop. But the SD fits in my pocket but the G1 requires a compact camera bag oer the shoulder. But the G1 can use many of the same accessories as the 10D (except lenses). Nuf said, eh?
Sorry for the tangental posting - I had to toss in my 2 bits in reply on the SD630.
Cheers!