Ok, so it seems the developer has kick up a bit of furore on this one..
Personally, I don't mind paying the £1.79 again to buy Tweetie 2 - at the end of the day it hardly breaks the bank. I'm not disgusted by it because he needs to keep making money somehow. (Although it looks like this developer may now be quite well off, judging by its ranking in the Top Grossing list

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But I do get this underwhelming feeling when I use Tweeite 2 - as it seems others do - and I think this stems from a few things:
1) In some ways, the new app is not 'better' than the first Tweetie - the UI is not so nice (an opinion), the speed is not so silky smooth (less of an opinion, bit more fact) and it doesn't even seem to do everything that Tweetie 1 did. In fact, I'm struggling to see - for my uses at least - what this version achieves that the first one didn't. And the implementation is not so nice either. What is the 'killer app' in version 2?
2) The idea that it was built from the ground up again. As the developer puts it - "I didn't just add a feature and change the version number. That's lame." Problem is, Tweetie 1 did not have any flaws or shortcomings in its implementation and was silky smooth and fast, at least for me. Tweetie 2 doesn't quite deliver that, which is why I'm left disappointed.
3) Tweetie 1 had 'wow' factor, Tweetie 2 doesn't.
4) The new icon is horrible (a matter of opinion, of course

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5) In deleting the first app from the store, Tweetie 1 has been end of life'd. Therefore, this version effectively stifles any upgrades to version 1, including any potential bug fixes.
6) The new version is underwhelming (did I say that already?

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Of course, one advantage of declaring Tweetie 2 as a whole new app is that it does give me the freedom to 'downgrade' back to Tweetie 1!!! I know which version of the app will be sitting on my iPhone's front page...