Given the speed of simple life forming on Earth, it seems plausible that it occurs elsewhere. The hard part comes when conditions exist to encourage more complicated life. And I suspect that given certain replicable conditions, complex life could exist.
The jump to sentient life is way harder.
Not only does it happen faster than I would anticipate, I don't see the difference between life and non-life as some dividing line that is hundreds of miles across. Really, what's that special about combinations of molecules that perpetuate themselves? Throw in a combination of molecules that produces some sort of animation, and a few other combinations that do things like improve detection of other molecules nearby (which atoms seem to do anyway), and next thing you know, you've got a combination of things that pulsate. Such a thing is simple enough that no special designer or natural meta-fluke has to be involved. Molecules just have affinities that make them combine in infinite ways. In a sense, evolution was taking place long before life began.
Yeah? Well what about the human eye? OK, I suppose that one could be a miracle, especially if it happened overnight, but the ability to detect light (in other words... eyesight) has been around much longer than man by a factor that requires the use of scientific notation. And primitive light detection systems are still in use today in lower life forms. Yeah, yeah. I know: "If humans evolved form lower life forms, why are there still lower life forms?" (now there is one impressive argument).
I remember being taught 6 universal characteristics of life back in grade school. I guess it was supposed to be a life detection kit, so while we were playing in the dirt, we could decide something was living rather than inert.
Enter sentience, the big <wahoo> of life. Now you just can't explain that <think Bill O'Reilly>, so I would propose another couple of characteristics that separate sentient life from non.
7. The obsession to glorify its own sentience, while at the same time,
8. Having no ability to understand its own sentience.
In fact, number 7 might be what separates man from the dolphins.
Not only do I think more life in the universe is inevitable. I also don't even think it's big a deal. If we ever detect sentient life elsewhere, the first thing we are going to do is figure out how to steal their inert stuff, which is really all we are after in the first place.