I'll do some investigation and see if I can spot an obvious problem, I'm pretty sure I tried all of these and they worked, but I may have broken things again.
currently in witter I do nothing at all with timestamps, I simply pull it from the message as it comes from twitter. To do more than that I can feel there might be a world of pain. I literally don't even treat them as timestamps at the moment just text.
One question though, are you using basic auth or oauth? At the moment basic auth still uses my own code for talking to twitter, and oauth uses the python-twitter library. It's possible that if you aren't using oauth yet, then doing so would resolve this issue, *if* the python-twitter library does more than me around timestamps.
I have honestly never used the favorite mechanism in twitter, and hence had not considered implementing it.
I'm wary of adding more tabs just because there are already a lot of controls. I'll guess I'll think about it, but honestly it is not high on my internal list of things that need doing.

For those that are interested in what the main things on that list are...
I'm working on bit.ly integration, to automatically expand bit.ly urls in my received tweets (currently working) and then support shortedning urls from a menu button probably.

better preferences - I've overhauled the preferences option to be a stacked window with pannable area, added a section for bit.ly credentials, swapped all the refresh interval controls to be touch selectors and generally made it easier for me to add new preferences.

once the above is all working I'll upload a version.

theme-support, I'd like to get it to the point that colour selection + icons can be bundled into a theme which makes it possible to create and separately distribute extra themes.

Account management - I'd like to tidy all this up into a sensible panel which let syou configure multiple twitter/ indentica/custom accounts. as well as bit.ly creds in one place. This requires a big change in the logic to support multiple log ins etc. but I can see the usefulness.

Lists support - Whilst I still don't really want to do avatars, I can see that lists address some of the issues that people have without avatars, namely the ability to focus in on specific subsets of their friends in an easy way.

I expect all of this to keep me busy for a long time. And if I get any good information on how to make better use of graphics libraries to speed things up, that will probably jump to the top of the list.