After kinking issues with quick-sets I'm now almost finished with my trial box of sure-t's and they've been good.
A few slightly uncomfortable sites (am more aware of them than quick-sets), but otherwise it's thumbs up. I am bit lazy and find the changing every two days thing a bit of a bore but for the security of no kinks it's an alright price to pay...
Regards the 640g I cannot say much - I only today swapped from paradigm to 640g (it's so retro looking! Like some resurrected mp3 player from year 2000) and so far it's all been exactly as before. But yeah, they were good on the paradigm and don't think the 640g makes any difference.
I've tried a few of the new angled mio30's but got a kink with them already, so not sure about those. Will probably give them another go as I would like to have an alternate (longer) option to the sure-t.