They are 24 1/8" long including the mounting brackets, 2 inches wide each. I have these with 2 T5's with really crummy reflectors and can keep high-light SPS down to 8" in my tank.
I have not tried them alone although I was running on only 1 LED strip plus the T5's for about 6 months while I dealt with a warranty issue on the other and most of my coral did OK. Since I have them both up and running everything is looking good!
I have seen other hobbiests make comparisons that a reefbrite strip is about the same usable light as 1.5-2 T5 bulbs but that is very anecdotal. I would guess that you should be fine keeping most beginner SPS near the top of the tank and corals with lower requirements further down.
Here's another thread about the reefbrite strips
http://www.canreef.com/vbulletin/showthread.php?t=66116
Also check out the link in my "for sale thread" that I linked to you for pictures of the exact lights so you can see what kind of colour you would be getting.