There are a couple of thread about them on ExPo (a search there should turn up some good info on them as well as home made models), reports are generally very good once you get past the price. It's supposedly well made and lasts and as noted, the ability to pressurize it is definitely a plus. If you build your own, add a Schrader valve 9typically to the fill cap) and you can add a few pounds of pressure with a bike pump for a much better stream. The main downside, besides the price, is that you're putting weight up high. I'm honestly surprised no one has added a 12v heating element to one yet; if they have, I haven't seen it.
I've thought about buying one or building one but for for my purposes, a simple 1gal pump sprayer works well enough (and I'm cheap). I fill it about halfway then dump hot water in to bring it to the temp I want. Take the wand part off and put the nozzle on the spray handle to make it short enough to be practical. When I was mountain biking a lot I'd keep it in the truck to rinse me and the bike but these days I just keep a
Simple Shower* in one of the camping totes that lives in the back. Add a one or two liter bottle and it's plenty for rinsing off or even a quick shower.
*No relation, I bought one when they were testing them out and first offered them on ExPo. It's been a great addition to the junk I normally carry and I used it a lot when I was living in the Philippines for rinsing off after surfing or swimming, hiking, etc. It's been to several countries now and I have a spare sitting with my other camping gear.
ETA- On those cheap solar bags (I also own one of the old Solar Shower brand), take the crappy push/pull head off and toss it in the trash. Replace with a sink sprayer from Lowe's/HD/etc.; the push/pull things always leak and they're a PITA to try to use with soapy hands or while holding a bike/dog/etc with the other.