A good point but luckily (very luckily), I have parking facilities at work that are mostly dry and mostly secure (otherwise I would be uncomfortable leaving it locked up outside work for both reasons)
My Swallow is on my commuter as it's also my Audax bike.
As Zipperhead says, leaving it outside in the rain isn't a problem as you can just put a bag on it, but I'd be unwilling to leave mine outside in case the saddle got nicked.
Luckily I have secure dry storage at home and at work. Brooks saddles really don't mind getting the twice daily soaking from a commute. It also gets a soaking for a couple of hours on a Tuesday night if I play football as I keep forgetting to put a plastic bag in my football kit bag. I've used mine for over a year now and only in the middle of summer did it need another lashing of proofide as it was getting a bit dry.
I don't think there's anything magic about why Brooks saddles are so comfy, because they are hard they force you to sit on your sit bones rather than being supported by the muscles near them. Once you've toughened up the sit bone area then you're fine. Other types of gel/cushioned saddles try and cushion your sitbones and work well until the muscles tire and pain starts when the non-toughened up bits come into hard contact with the saddle.
For what it's worth, after years of Brooks riding, I can now do 100km+ rides on a saddle that used to be a complete ass-hatchet so there might be some truth in the old saying that you don't break in a Brooks, the Brooks breaks you in.
If you're used to spending hours in the saddle then it shouldn't be too much of a shock.
Of course, some people just don't get along with them, probably because they are just the wrong shape for this type of saddle. Also, the sizes vary quite a bit. The swallow is considerably narrower than the B17 Wide so you may want to try a few.
