You have to balance the accuracy of the tuner with what you're actually trying to accomplish. For playing, rehearsing, gigs and most recording in a rock band context- the Boss is great. What you get for the price of the Boss is a stable, buffered, and exceptionally rugged tuner that doubles as a mute.
When I recorded at a world class studio (where many songs you've heard bunches of times were recorded) they RECOMMENDED that you use the house Sabine ST-1100. Not the most accurate of tuners...
The tuner in my bass rack is a Korg DT-2. Either it's crappy or "too accurate." What I mean by that is that I spend far too much time bouncing between flat and sharp and not enough being "on." In the end, I always end up "ballparking" it- so it's in the neighborhood of in tune. I don't like that tuner much. I do, however love the Boss TU-2- I've owned mine since 1998 or so and have had no issues with it whatsoever.
Most everyone that has a Peterson swears by it, I don't think I can justify $200 on a tuner, when the additional accuracy is a non-issue to 99% of the people that will hear what you're playing. Unless you do setups for a living or are recording with absolute clear and precise pitch, the Boss is a great choice.