I'd agree an absurd number of money bags have been filled by MS's OS and Office products over the years, dwarfing the profits of other operations. That speaks more about the runaway market success of Windows and Office than it does about lack of profit elsewhere.
I like that MS tries different things over the years. Yep, their early smartphone OS sucked, so much clunkier than Palm OS and horrible battery life. Xbox is only recently profitable, largely because of the Red Ring of Death fiasco. I had higher hopes for Zune, as the hardware was competitive. Looks like iTunes ate their musical lunch. Bing was strong effort in the search market. Not sure why that flagged. People already mentioned Visual Studio. Their tools survived and grew while so many others stagnated.
Not everything was organic growth. They bought companies like Visio, Hotmail, Bungee, and Skype (just for a tiny sample of better-known names).
At this point I think Surface Pro is going to be a failure. I had reserved judgement but they recently leaked a 4-odd hour battery life. If true, that won't cut it. 1.x pound tablets are pushing 10 hours (iPad is amazing there) and higher-peformance 2.x pound laptops are pushing 8 hours. I'm not seeing the use case of this over either a tablet or a high-end 12 to 13" notebook, depending on your need.
In other words, what sets Surface Pro apart from the many poor-sales tablet PC's that came before it? Lenovo had killer tablet PC's for a long time now, say the X220T (now X230T). One answer is Windows 8 but that is not unique to Surface Pro. Slightly lower weight? Tablet-mania?