Well, I have an iPod 5, so I assume I can fit in here, considering it has the same specs as the iPhone 4S. Anyway, I'm updating my iPad mini with Retina and my iPod 5 from day one. I don't like my Galaxy S4 (and will possibly end up switching to the iPhone 6) so I use my iPod and iPad more. I see myself using the iOS 8 features a lot, lag or no lag. Also, I'm thinking the iPod 5 will get Handoff since it supports AirDrop and has the updated whatever it is that allows that, something that the iPhone 4S doesn't have. I see myself using it a lot, and am pretty excited. Will make for much easier switching when my iPad is dying or something, and I am reading something on Safari.
I have updated from day one several times and have never had problems, so that's what I'm going to do. Even though I haven't had problems in the past, (other than errors when trying to verify the update because of such heavy traffic) I still fully expect them, and am prepared for what may arise.