Rather than paraphrase him, I'll paste what he's already said quite well:
First of all, 2.0 is a free upgrade, so I won't miss out on any upgrade fees from people that want to stay on Panther or Tiger.
Secondly, roughly 90% of my users are early adopters and have in all likelihood upgraded to Leopard within a few months of its release, so by keeping compatibility with older operating systems I am catering to less than 10% of my users.
Thirdly, it has a significant cost to stay backwards compatible, this price is paid in the form of:
- Time spent debugging (and sometimes making workarounds for) issues only present on the older OS version.
- Time spent implementing stuff that Apple offers for free on the new version of the OS.
- Not being able to make use of features only present on latest version of the OS when it's too impractical to conditionally make use of them.
- Code complexity, because it needs to do different things on different versions of the OS.
Is eliminating those costs worth a 10% drop in sales? You bet they are! The reason why I have kept Panther compatibility for this long has nothing to do with additional sales and all to do with me just not liking to cut people off.
I think Allan defends his decision quite well. Much better than Adobe does, in regard to Soundbooth's lack of PowerPC support. There's more to Allan's statement, but you should hop over to his blog to read the rest of it and let him know your thoughts on the issue.
To balance any potential backlash, Macromates will surely win a few hearts and minds by the free TextMate 2.0 upgrade. Any other TextMate users out there have an opinion on this?