Eh, it's not the only thing I find wrong with Tumblr, and I'm yet to try out your latest release (stepped on debit card, broke it, cancelled it, iTunes charge failed, no upgrade for me)
Please try going native, the performance increase would be in the order of magnitudes.
I'm not the only one but it's a very small team at the moment. We have ambitious goals that we're aggressively working towards though.
Tumblr content can be quite diverse and often contains arbitrary user-inputted HTML, numerous inline images, etc. It's non-trivial to render but as I mentioned, we're working hard to provide an even better mobile experience.
Please try going native, the performance increase would be in the order of magnitudes.
Are you the only one working on the app?