Ah that is very true! I mainly watch movies and browse the net so 1 hour really won't make that big of a differenceI see your main concern is the extra battery life. Well, according to this review: http://gizmodo.com/5287179/macbook-pro-2009-review yes, you do get more battery life, but with a workload of watching video files, you just get roughly 1 hour more for with new 15" Pro. (Admittedly with a lighter workload the delta would be longer but I doubt 3 hours!)
I've tested it myself by looping the 1080p Star Trek trailer and I got a result very similar to theirs; 2 hrs 50 mins for my late '08 MBP. So the reviewers got 3 hrs 46 mins; 1 hr more. Get yourself a cheap 2nd battery from eBay for US$85 and boom, 5 hrs 40 mins of playback time and you beat the new MBPs by a mile. And if you have a lighter workload, a 2nd battery would give you much more than 2 extra hours on your current MBP compared to the new ones. If you make use of this feature, you'll have no battery envy. But if you're not interested in carrying a 2nd battery, I understand your wishing to upgrade.
For what it's worth, you currently get full 3 gigabit SATA II speeds compared to the newer's capped 1.5 gigabit SATA speeds. AND when USB 3 comes out, you should be able to get an expresscard for your MBP while the new ones can't. And changing batteries on the late '08 MBPs is so much easier, quicker and cheaper! It seems you'll be racking up charge cycles on your MBP batteries.
Plus I can see your point with getting a second battery. That is something to consider.
Thank you