I have both machines and use them daily
Both are strong and capable machines. My 2008 15-in 3,1 2.4 Ghz C2D MBP has been upgraded to six gigs of ram (yes it recognizes and uses it all in spite of Apple's official specs) and a 750 GB Scorpio Black 7200 rpm hardrive, then a clean install of the OS and all apps, so she's a fast, capable machine that is handling everything I throw at it with ease. Granted, I'm not doing much video encoding, but it does well enough when i do. MS Office 2011 apps start virtually instantly, and CS4 apps are quite acceptable. Upgrades followed a replaced logic board and new 4 GB of ram by Apple, so it's virtually a new machine. It took the Lion upgrade without a hiccup and actually seems faster. It is now used as a nearly-dedicated desktop, with an aluminum laptop stand that suspends if off the desk for better cooling, a 24" IPS monitor, three external drives, a USB hub, speakers, and ethernet to my Airport Extreme. When the new MBPs came out and MicroCenter promoted a $999 deal on the new base 13" MBP, I snatched it up to be my go-anywhere, do anything machine. More powerful and quicker than my older machine and more portable too, its easily the best computer I've ever had -- and i"m sitting next to quad-core windows 7 machine with a full gig of gpu memory that I never even bother to boot up anymore.
I'm happy with this setup, though am getting into more high-end photo editing and experimenting with video work. We'll see how this two-machine setup continues to work, though the new 13" still has substantial room for upgrades (I could drop in a 7200 rpm hdd and at least 8 gb of ram - even 16 gb if the prices come down)