Well that sounds about right. That's the same sort of 4-year gap that I tend to stick to. The good thing about the 13" MBP is that they're basically required to keep the price lower. It's funny, though. We're in a point in time where for 90% of uses, the C2D CPUs from older Macs (or any PC for that matter) are fine. So that 2008 MBP would be fine for a non-power-user. On the other hand, the amount of people I've seen trying to keep a 10-year old PC running is astounding.
We have finite download limits here, so I much prefer to keep content locally than stream it. Audio's quite negligible, but still.
there's been rumor that a 13" retina might be in line to come out along with an iMac upgrade either later this year, or more probably next year at this time. I felt this was a worthwhile upgrade, as my last laptop was an early 2008 MBP. besides, my older brother bought my old pro anyway (he doesn't really care bout latest or greatest as long as it works, which it does)
Music isn't as big of an issue with me I have all my iTunes music available on my iphone when I want it and I've gotten by with the desktop app for Spotify that lets me listen to any songs I want anyway. (since I have it on my desktop Mac too, it syncs up the iTunes playlists it gathered from iTunes as well.)
I suppose if you don't keep media on there, it's not an issue. I could handle keeping movies and ISOs elsewhere, but music is one of those things I want direct access too. Plus, it gets a little fiddly when iTunes is pointing to stuff that's not always there...
Good to hear you're enjoying it. I daresay there'll be a 13-Inch variant in 2 years time when I upgrade from my 2010 MBP. In the meantime, I'll get myself a 120GB SSD and Optibay adaptor near the end of the year to give it a bit of a boost.
I've seen those 1:1 hacks, but honestly just using the highest scaling option is good enough for when I really need the real estate. I usually just keep it at the retina setting or the second option. as for space, I find 256 to be plenty for system/apps/current documents. I offload all irrelevant files to my mac pro when I'm not using them and I don't keep music or videos on it either. (media is what the external is for)
That being said this thing is fast, (even when running Win7 in VMware.