I really need upload files bigger that 1 Mb, so i only have the Blobstore API. But any use it in production? know any issue or problems?
I've used the Google-internal equivalent happily (I work for Google), but the externally-available Blobstore is explicitly tagged as "an experimental feature" in the docs -- "the API and behavior of the service may change in ways that are not compatible with earlier releases, even for minor releases of the runtime environments" is how the same docs translate this "experimental feature".
For most definitions of "use in production", I guess this "may change in ways that are not compatible" would mean the answer has to be "no", alas. If you're an exceptionally agile and nimble development shop, able and willing to change the API around as needed, maybe. Otherwise, I'd recommend setting up a separate "pilot project" to explore the current offering and not depend on it (yet) on your "production" (revenue-generating, mission-critical, etc) project!
But, no, I do not know of any issues or problems with Blobstore, except for that "experimental" tag... which, however, has its importance!-)