I helped a friend edit some wedding photos over the weekend. In the middle of the job, I noticed that the colors were off on both my monitors. It's been some time since I calibrated them, so out came the i1 v2. It took several tries before the software recognized the device, and the results had an orange tint on my LCD and a green tint on my CRT (and yes I could see it even if I'm partially red-green color blind). So out came the i1 v1, and now the calibration was acceptable.
Both i1's are technology that's several years old. I looked around and decided that a Spyder3 Elite would be a good upgrade. I found one for a decent price on Amazon, and I was surprised to find it at my door within a day!
Out of the box, the Spyder seems flimsy. The cable is thin, not a good sign compared to the i1. There are also chrome surfaces, which never work on anything you have to touch. It also feels light, which makes it prone to moving when it's on a monitor. There's a detachable suction cup for attaching it to a CRT screen, but the cup looks cheap and doesn't work well; the Spyder fell off my CRT three time during use.
The software is not very user-friendly. I had to dig into it to figure out how to let it allow me to use the RGB controls on my monitors. I'm used to the i1's software, where you either pick the easy option (software compensates for everything) or the advanced (user adjusts everything). The software doesn't measure in real time; you have to tell it to measure after making adjustments. The i1 software shows the new measurements as you change settings, which makes calibration much faster. You don't have a choice on where to locate the sensor; it's smack in the middle of the screen, and moving the window just snaps it back to the center.
However, the results are much better with the Spyder. This is the first time I've had both monitors give me the same color and brightness (verified by having the same photo on both monitors).
To conclude, the Spyder is the better of the two devices in terms of results, but the i1 is the more user-friendly device.