Those are good bikes and you probably won't have any big troubles out of it. You can save a slight bit of money commuting with it but only if you do all the work to it yourself.
My bike is a dr650 and it is comparable in size and stuff to the bmw but it gets probably 10mpg less due to being 80's tech. I get consistently 50mpg. I run D606 knobby tires @ $125 a pair I mount them myself and get about 5,000 miles rear 10,000 front on a set. I do my own oil changes at 5-6000 miles. Insurance on it is 63 bucks a year full coverage, $500,000 limit and roadside assistance.
But the big expense is the good riding gear. Get something with cordura and CE rated impact padding. You are probably looking at around $1000 for boots, pants, jacket, gloves, and a good helmet that can handle a 35mph low side without getting a scratch on you.
Then you are looking at 15 minutes to gear up and 15 minutes to get it off and you have to have somewhere to stuff it all at work. With good gear it is usually waterproof so you don't really need rain gear for less than an hour or two of hard rain. Just zip up the air vents and keep riding.
So overall I think it is worth it. If you don't think it is, go over to advrider.com and you will change your mind
