Different problems can be caused by different things, i can’t imagine every problem is directly a result of a WordPress upgrade.
I write and mod plugins (for fun and to learn), and i don’t have any compatibility problems under 2.8 + all the way upto 3.0 … (i use the most recent (betas etc..) on my local install – stable version on live site)..
There can be alot of differences between how functions behave in PHP between versions (same can be said for mysql), something as simple as one version number can be the difference between functionality and errors. It’s impossible to have a totally bug free piece of software (well i’m yet to see any such software in my lifetime), there’s just to many variables (unknown factors) to conclusively point at one area as being a cause of a problem.
Software can only be soo smart, it’s going to fail somewhere. You can write and write for every possible scenario you can imagine, but you can still bet some average joe out there finds a way to make your software break, it’s just the way it goes.
Good software either a) rarely needs an update, or b) receives them as often as they are required. If you find the delay between WordPress versions and plugin updates too much, then you need to consider alternatives to ones that receive minimal updates and cause the most problems.
For the most part, plugins shouldn’t break after an update. I’ve not had a broken plugin since, i think.. early 2.8, but maybe 2.7 .. auto upgraded each time since 2.7 … and that was a downloaded plugin that never worked anyhow…
Just because it’s available as a plugin doesn’t means it’s written to the same standard as WordPress (just something to consider – i’ve seen shocking code in a few plugins).