I have two variations of the Houdini, from 2010 & 2011. They both work well ih Hawaii weather, where it can be cool with sporadic showers. However, I would not wear them as rain gear in sustained downpours or prolonged temperature drops.
As stated elsewhere in this thread, Patagonia does a god job of stating the type of fit, ie slim, fitted or roomy for their clothing. That said, I still range between XS to M for their gear. Also, the Houdini, and most other manufacters' gear I've tried or studied will be sized to accommodate garments underneath or not and the sizing will depend upon this design element. So it's important to note this when shopping, especially online.
As far as standard sizing, most products sold internationally will state the size under each system. Usually, manufacturers who sell in multiple markets will size and advertise accordingly, even though sometimes sizing can still be a bit "off" if it is not what one is used to, so it's not a matter of right or wrong, much less demanding one worldwide standard.
As far as being annoying to order something and have to return it because the fit per size is not what we're used to, yes, it is! Unfortunately, this is just a necessary evil of not being able try things on in advance. How many of us bypass our local gear store to shop online, causing the local store to close? Not to mention what women routinely encounter when garments and gear are sold as the ubiquitous unisex! where the garment dimensions really don't fit anyone very well, or it's really just a man's fitted garment that is re-labelled to lure women into buying it. Sometimes I think the shipping charges make up the online savings as compared to shopping local.
Alas, the global marketplace! However, on balance, things usually work out, after all, we all get to come here and talk story.