[foldr]

Most of my projects are built around interfacing microcontrollers with I2C sensors. I've never had too many problems getting I2C communications working. I think a lot of it is psychological. Without a logic analyzer you can feel a bit helpless when you're not succeeding in connecting to an I2C peripheral. However, there's only a few things that plausibly can be going wrong with something as simple as I2C. (You have the wrong address, you have it wired up wrong, or you're misusing the uc's I2C peripheral.) It's quite feasible just to work through that list of possibilities until you find what's wrong. It does require a certain amount of faith, as you generally see no indication of progress at all until you get it working.

I'm not denying at all that a logic analyzer can be helpful. I'd just encourage people who can't justify the expense to have a try without one.

Edit: That said, I see that low-end logic analyzers are actually pretty cheap. I should probably get one!

[milesvp]

Low end analyzers are good for slow signals. 24Mhz is a common sampling rate for less than $30. Just remember that your bus needs to be less than half that speed, and even then the analyzer may lie to you if your bus speed is anywhere near half your sample rate. Also the timings in your bus can greatly effect what the logic analyzer will show vs what the cpu sees. I had a false positive last week when I should have just looked at the rx the cpu was seeing when trying to get an SPI peripheral working on a new chip.

So I may be in the market for a better analyzer soon. But all in all my $30 was a good investment, and has made it easier to setup new serial protocols.