When it comes to tankless electric water heater reviews, like many other product reviews, you need to keep in mind what exactly it is that you are looking for. After all, most reviewers have a tendency to get carried away if they are really impressed with a product - HiFi reviewers always seem to recommend costly units that are technically impressive. Perhaps this quality is not necessary for most non-expert users...
It is sort of the same with electrical instant hot water heaters. There are some truly remarkable units available - built using space-age technology that NASA use to launch the shuttle. But you might not really need to splash out on something like that.
The first thing you should look at before investing in a tankless waterheater is the value you will get from it. Some home set ups will be better served upgrading the electric water tank to one of the very efficient modern units.
Of course where space is an issue an electric tankless water heater might be exactly the thing. So be clear about what you are going to use it for. If it is going to be used exclusively as a booster for hot water in the laundry room then find out what the maximum demand will be (this is the maximum flow in gallons per minute) and buy a unit that matches this. Just like any other product, you simply need to decide how much you are prepared to pay and do not go over that price.