not enough data points to say for sure there's a noticeable decrease. we have a decent amount of variability here (newborn, toddler, parents that come for extended visits), so there's some ups and downs from that. plus, random remodeling projects too. i think i will know more after may and june because those are months with no heating or cooling needs around here (generally) and we don't have guests. we heat with firewood, so winter usage is actually lower than spring usage on the electric bill.
i didn't vent it to the outside. in the winter, especially during our cold snap where we were in the 20s for a few weeks, i thought about it b/c it definitely felt colder, but, in hindsight, i think it was feeling colder b/c the air was conditioned and dry. now, with temps in the 50s-70s, i barely notice it in the garage. i don't think the venting will be worth it.
i think the product is probably awesome if you live somewhere warm all the time (FL, CA, TX) b/c you could vent the air to your living space and get 'free' a/c. in the winter, the efficiency drops a lot when cold.
also, the first hour rating on this apparently does not provide enough for our needs in the winter. i don't know if it was coincident with guests, but we did run out of hot water several times. we have since adjusted the water temp up to 124F, so while that's a workaround, it's not really ideal either. the bigger units they sell have nominally large first hour ratings, but are considerably more expensive and the theoretical breakeven point is much further in the future.
knowing what i do now, i probably would not purchase again. standard electric water heaters are a known element and super easy to plug and play. this had some screwing around - not horrible, but still. and, it sounds like new technology and understanding even within rheem tech support, so a lot of variables there. if it lasts 10 years, i'm sure i'll be happy. if not, well...