From what I've read the weak links in the 4L30 are the selector switch and solenoid issues.

I bought my VX with 162k on the dial. It had a failed transmission that had been "fixed" and when the fix failed a used Trooper tranny was installed. It never shifted very well for me and seemed to slip and hard shift in cold weather. That was as good an excuse as any for me to do the 5 spd swap and I am very pleased with the result. It really woke up the performance making the engine feel more powerful. There are of course trade offs, I have a lower final drive ratio in 1st which makes for better engine braking when wheeling but it is more difficult to crawl out of sticky situations without stalling. I love the VX as a manual though but it is definitely a personal preference.