"The" site to get information on these boas is www.kingsnake.com/candoia/ by Jerry Conway. He's pretty much the end-all-be-all of Canodoia and has kept and bred them longer than anyone else I've ever heard of. While I don't keep viper boas, I do have four Solomon Island ground boas and one Santa Isabel ground boa. The personalities vary - of the five I have, two are quite docile, two tolerate handling, and one is Satan's daughter. lol To be fair, the aggressive one was wild caught when I bought her and has acclimated to captivity pretty well except for the handling thing...it's just a no-go with her.
I have read that the viper boas tend to be a bit nippier than some of the other Candoia, but that is really something of an individual trait. As for feeding on mice, in my limited experience I've found the older animals will pretty readily eat rodents as prey and it is more the juveniles that are adamant about alternative prey items such as lizards and frogs. Even so, I would insist on seeing it feed prior to purchasing it. On the same token, I would also insist on handling it prior to purchasing it. There's no need to purchase it if you want an absolutely calm snake and that one isn't. I've found that even the ones that are more shy will calm down with gentle handling (with the exception of that one female). Because most - though not all - of the Candoia stay small, they don't need large enclosures. Except for my two juveniles, mine are currently kept in tubs that measure roughly 22" X 16" X 7" (if I remember the measurements correctly anyway) and do quite well. As my females mature, they should have a slighly larger enclosure - probably one of the 3' length cages would be fine. They're great little snakes and if you have some experience keeping other boas or pythons, I'd gladly recommend them as something a bit different and interesting to keep. They're greatly under-rated in my book, but also not a group I'd recommend for the beginner.
Raven