Sorry in advance for wall of text/tangent.
I, too, have had mixed results from iTM. I subscribed in March, and matched/uploaded my library without an issue.
Had a HDD physically fail during a Time Machine Backup, corrupting the TM. Boy, was I ever thankful for iTM that day. I had redundant backups of other files, but my media would have been lost, save for what was on my mobile devices.
Later, though, I had issues with songs not downloading from the cloud: songs that had matched and also songs that had been uploaded. A few days pass, and this is resolved.
Apple has been vertically integrated for some time for other things, but not so much with internet-related services. OS X running on their custom designed hardware, the "Walled-garden" approach to iOS, etc. This is one reason we expect things to just work from Apple, because they have control of every step of the process (arguments can be made that they don't control everything, like Intel's chip production, but you get what I'm saying). When something is released, the physical product and the user experience matches what (I imagine) Apple envisioned it to be, considering technological limitations.
This has not been the case with internet services. Obviously they've taken great steps with starting the Maiden, NC and Prineville, OR data centers, but to me, it seems like this has been done in a step-wise fashion, with some things being rolled out before the final, visualized product is complete. See .mac, iWork, MobileMe.
I really like iCloud. In terms of keeping my devices on the same page (literally with iOS 6 and ML's Safari iCloud Tabs), and tools available to developers to use storage in the cloud, I think it's great. iTM and the new Podcasts app, however, seem to fall short. As the complexity of the products and services offered continues to grow, it's even more important to provide transparency when a known issue exists, as there are so many places where something could go wrong.
Eh, but the fanboy in me says I'm sure they have their reasons that they're traditionally tightlipped about pretty much everything, I'll trust them to fix this As Soon As Possible.