Avoid Silver Deep in Providenciales. My Dad and I had a poor experience with them in late 2004 (so things could have changed, but I doubt it--their website hasn't changed).
We did two half days. The first went well enough. My Dad caught a smallish bonefish, though it was sheer luck. We almost ran over the fish and my dad flipped the fly at it just in time. We had some shots, but the fishing wasn't anything special.
We went with the same guide on the second day, and his inexperience really started to show. He got us stuck back in a lagoon because he wasn't paying attention to the tide. When he finally got us up on plane, he ran the boat into the mangroves (no damage, but too close of a call).
After that, he decided to make a long run against the tide/wind to another spot--trying to make up for the wasted time in the lagoon. But by the time we got to the next spot, the sun was low and fish spotting was near impossible. We fished for an hour or so unsuccessfully and then went back. The tide and wind had shifted, so we got beat up even worse on the way back. We were soaked, wind burnt, and sore with nothing to show for it.
We really hadn't had any decent shots. That happens when you waste more than half of a half day trip. The part that made us really sore was that the rates were exorbitant. I think they were asking something like $750 for a full day--and this was in 2004. The half day was probably in the $400-$500 range if I remember correctly. When a guide is charging that much, you expect a top notch experience.
We booked the two half days based on an advertised discount--booking multiple trips would get you something like 20% off your second trip (my memory is foggy). When we mentioned the discount, we were told that it didn't apply and that they could give us a free t-shirt instead. The woman running the show, Paola, was extremely rude about it.
We couldn't press the issue much more because she had to give us a ride back to our hotel. My Dad and I have probably fished with numerous guides, and only once have we had a worse experience (guide showed up late and smelling like booze in the Keys). A lot of people have great things to say about Silver Deep, so maybe we caught them on a bad few days. Still, I'd look for someone else or DIY.