There are three running themes to those people who believe the price of a 3.0 upgrade is unjustified.
1) R# is so unstable you should give it to us for free because we've had to smell your crap for this long.
2) I just go through paying $150 for a personal version, and now you want me to pay for an upgrade 6 months later.
3) There aren't enough changes in 3.0 to justify it being a full version release for c# users, and since I won't be using VB.net, then I won't want the few features that made it in for us "real" programmers.
To those I give my two cents --
I understand your frustration with the 2.5.x version and the decision to make users pay for the upgrade to 3, but honestly -- some R# users (myself being one) haven't had to pay for upgrades since 1.5, and only paid 99$ then. About the instabilities of 2.5.2, I am not sure what problems you people are having, but I don't, and imagine a large portion of the R# community do not have those issues. I do have one nagging one (the exception on solution close), but I think that's hardly a reason for you guys to be so pessimistic. If you haven't downloaded and played with 3.0, then yes you probably would think "there are hardly any noticable updates", but I beg to differ.
3.0 is not just simply a re-hashed bug-fixed 2.5, there are significant improvements in coding suggestions, different levels of warnings for code inspection (suggestion vs. warning). There are a considerable number of new suggestions, the new code formatter, better XML support (and yes, VB.NET, though I personally won't use it)...
Todo Explorer, the Navigate to Symbol, Refactorings like Replace Constructor with Factory method, Find Referenced Code (not just find usages, but the other way around!), the Unit Test Explorer.
I promise I'm not a paid JetBrains hack, but I believe in this stuff, and I know it has been very useful to me.
I guess what it comes down to for me is -- JetBrains has never said "free upgrades for life", unlike other notable companies who have had to renig on their promises (We're looking at you WinZip and SiteDesigner!), but instead have been gracious enough to provide its users with a great product (even if its in development most of the time) for a great value. First Version 1.5, then 2.0, then 2.5... That is like getting a 2005 car, then the company giving you a 2006 and a 2007, while they all may have their own quirks and shortcomings, that does not give you the right to expect a 2008 for free.
I guess what I'm saying is quit whining. There are plenty of products on the market, and for you to whine about a $150 upgrade is pretty rediculous. And if you think the grass is greener (more stable) on the other side, feel free to give it a whirl, and I suspect you will find it not only just as unstable, but limiting as well.
Just my 2C worth.