But hey, if you want to use tantalum and I don't then what's the big deal? Frankly, I am sorry I ever commented to this thread and will definitely think twice about relaying my experience here in the future. I really have spent way more time here on this than is warranted. Good day.
At least it made this thread lively and encouraged many to come up with the right docs to answer OP question.
Indeed. Thanks for all the replies.
Although it may look like the manufacturers are selling (e.g.) 25 V tantalums as 50 V and then telling you to not go above 25 V to be safe, that's not the case.
Take the time to read one of the linked documents and it becomes clear why that is. I also know now why we saw a temporary increase in failures when we went leadfree, the solder process is an important factor in tantalum reliability. This went back to normal as soon as the insufficiently derated tantalums were corrected in the designs.
Infant failure rate of tantalums is higher than that of electrolytic caps, but as the lifetime progresses the failure rate of electyrolytics gets progressively worse while tantalums stay pretty stable. Long term, tantalums beat electrolytics. So I tend to agree why those that use tantalums the right way say that they're relaible. It is also my own experience in industrial electronics in which tantalum capacitors are still very common.
All types of capacitor have their place. It is likely, though, that new designs avoid the use of tantalums, but as I wrote before, that may be more of a result of rising prices of tantalum capacitors and the availability of (now cheaper) alternatives rather than bad reliability.