I uninstalled after four hours on my Bionic. The battery usage graph showed it using 79% of the battery power... four times as much as all other services combined!
I've read on other forums that it doesn't play nicely with the Bionic. I have to agree.
It's pretty chicken-scratch to blame the issue on the OS. The developer's website also says he only has a Nexus One for testing, which means Screebl was developed for a phone that's now two generations old.
With Screebl installed, the screen off, and no activity whatsoever, my phone goes from 100% charged to a critical battery shutoff in about four hours. Without Screebl, it will run for 12+ hours with moderate use.
Frankly, I don't care whether the battery is really completely discharged in four hours, or if Screebl just causes erroneous readings that cause the phone to shut down because it APPEARS to be discharged. If the app doesn't work with new devices and the latest OS, then it's defective.