I- like you- also have the old version. The key (tangible) benefits to the new one as I see them for your situation:
- 720p30fps vs. our 720p24fps. If you have much 720p content, yes, this is only 6 frames per second better, but it might make the difference for some video stuttering in 720p.
- An apparently great implementation of Netflix (in Apple's typical "grandma proof" simplicity)
- The Airplay feature if you have an iDevice and think you'll use that feature, or if you often have people over with iDevices and you think they'll use that feature
- Faster UI- early videos make it appear that the UI will be a lot faster/crisp, which makes sense on newer hardware. My Apple TV UI tends to lag often- sometimes for several seconds between remote commands
- Ongoing enhancements appear to be solely associated with the new version. Ours are apparently "end of life" with regards to software updates. If there every is an App store, our version is unlikely to get it. If there is a Hulu Plus, CinemaNOW, Vudu, etc implementation (like they added Netflix this time), our version is unlikely to get any of that... unless we apply the hacks to add Boxee, etc.
I don't see box size as a benefit at all, except to a few guys excited that it will hide behind their wall mounted TV (though it might be challenging to control it there).
All that said, I'm not yet convinced to replace the classic version. I would miss local (sync) storage vs. streaming everything, so I hope that Apple issues a software update to normalize that USB port, so that we could plug in our own storage, hopefully at whatever size storage we desire. That would be huge... and only a software update. The hackers easily did this with our old version, so it is hopefully possible with the new one too.
I would have bought as is if it had 1080p hardware, even if there was nothing to rent from iTunes, Netflix, etc. I continue to hope that we soon find out that Apple just chose not to announce that benefit. We should know that within a few days (but I'm not expecting it- just hoping for it).
Given your situation though, unless something in the above list is really important to you, what you have is probably still good enough. It is for me... for now.