I got back a response today from Coriolis re: compatibility and future upgrades for iPartition. Here it is for those interested:
Q: I am very interested in purchasing iPartition. However, I have been hesitant to do so because of an incompatibility problem with Leopard
10.5.1. I see that you now have a workaround for the bug in 10.5.1. An
earlier FAQ indicated that there would be a performance impact to
using this workaround. Just how bad is the impact?
A: It really depends on the system. I haven't measured the read/write performance for ages now, but I remember the difference between reading 64KB at a time and reading 16MB at a time was fairly significant. It's difficult to generalise though; if I had to guess, I'd say that for modern systems it's probably of the order of 5-10%, which in the worst case could make a difference of as much as 40 minutes or so to the run-time. Usually it would have less impact than that (it depends on the layout of files on the disk, amongst other things).
Q: Also, once Apple issues the much anticipated 10.5.2 in the coming
weeks, I presume the bug will have been resolved.
A: I strongly suspect that we'll have to wait until 10.5.3, actually. But as the
e-mail I sent around earlier said, we don't have any official information.
Q: However, I don't want to have to buy another upgrade of iPartition that
performs better with 10.5.2 without the bug problem.
A: You wouldn't have to. We use the usual scheme for version numbering, hereby you only pay for upgrades when the *first* number changes (i.e. an upgrade from 3.0.1 to 3.0.2 or even 3.9.12 would be free; an upgrade from 3.0.1 to 4.0.0 would be chargeable). I'm always surprised by how often we're asked this kind of question, since AFAIK just about everyone does things this way
Q: Are you planning on providing current purchasers of iPartition with a free upgrade in that instance?
A: In case the previous answer didn't make it clear enough, yes, we are.