I went for the 2.53GHz.
In Canada, it was like $300 more. It would cost me $70 CAD for the RAM, $56 for the HDD, and then I was basically paying only $180 more for a third of 1GHz increase. Seemed worthwhile to me.
You can always upgrade the RAM, HDD, etc. down the line, but the processor you're stuck with. Might as well go big in the beginning.
Plus, I could have gone with an Intel SSD or something from the price savings, but with the max being 160GB for a lot of money, I'll hold out for the 300GB coming in Q1 2010 likely for the same price or cheaper. That way when it comes out I won't be punching myself for spending half a thousand dollars for an SSD made obsolete four months from purchase.
SSDs aren't quite worth it yet, IMO.
Above all, though, before this 13" MBP I had 2.4GHz MacBook Unibody (solely upgrade from 2.0->2.4 for the backlit keyboard) and I couldn't see myself downgrading.