I don't have any experience with Teak for guitar/bass parts, but I built a goodly amount of deck furniture out of it. Working it felt a lot like Mahogany. In fact, it's difficult to tell the difference unless somebody points it out. Weight, grain, density, color, etc. are all similar, although it the grain is a bit tighter. It's fairly light and pleasantly colored (again, much like Mahogany). So, I'd expect it to behave much the same way in an instrument. But, I'm just guessing.
I remember when I built that stuff, everybody said "don't finish it!" so I didn't. It was gorgeous as built, and finishing is always a pain in the ass, so it was easy advice to take. But, it turned gray fairly fast. I imagine that might have had something to do with leaving it outside all the time. The sun is hard on just about anything. I can't imagine you'd have the same problem with a guitar/bass unless you left it in the sun/rain/snow for a couple years. But, that's where the wood is headed colorwise over time. Might keep it in mind when choosing a body finish.