Rabbi Nimchinsky below gives an excellent summary of the various pros and cons of SmartBoards, much of which I had corroborated via my own research. The Tablet PC idea is a new one to me, though, and I decided to do some independent research to see what other alternatives there were.
Here's what I came up with. I'd appreciate any comments or corrections!
There seem to be three basic setups that are available:
1. An interactive whiteboard (such as a SmartBoard) at the front of the room. Teachers and students all have to go up to the front to use it. This restricts the teacher to the front of the room and unless you have a wall mounted projector you'll have to deal with the shadow issues mentioned by Rabbi Nimchinsky. The projector can also be easily be bumped, etc. Everyone I've spoken to has recommended the wall-mount version to avoid these problems.
2. An interactive whiteboard (such as a SmartBoard) at the front of the room together with a wireless controller pad that allows for teacher interaction from anywhere in the room. Smart offers an Airliner; there is another company, Interwrite, that has a similar product. These are plastic, relatively cheap (about $400), very durable, and can be easily passed around and ported from person to person. Both student and teacher can interact with the Smartboard at the same time--the student from the front of the room, the teacher from the wireless pad.
Cons--the wireless pad does have a learning curve, since it's essentially a blank plastic screen with a pen. You need to learn how to navigate the pad while staring straight ahead at the SmartBoard--nothing appears on the pad itself. It's not that much different than learning to use a mouse, but it does require practice.
An intriguing option here is using a Tablet PC as the controlling computer and walking around the room with that. This would require an interactive whiteboard that offers Bluetooth connectivity for the controlling computer. I don't know if Smart offers this option; Interwrite definitely does. (Interwrite sells an interactive whiteboard in addition to its wireless slates.) The advantages to this is that you don't have to learn how to use a slate--you see everything on the screen right there and it's duplicated on the whiteboard. The biggest con I can see is that the Tablet PC is much less durable and I'd be nervous about dropping it. I get really involved when I'm teaching and I don't want to gesture with a Tablet PC in my hand!
3. Finally, if interactivity from the whiteboard itself is not a big concern, you can use a computer with a projector, a regular whiteboard, and a Tablet PC. The projector would need to be a wireless model to receive signals directly from the Tablet PC. The con here is that only the teacher can do anything with it.
You can create a network and give students Tablet PC's too but that will rapidly get expensive and you'll have to be concerned about breakage. I can see that working in a college classroom--I would be hesitant with younger students.
A cheaper option is to use a computer with a projector, a regular whiteboard, and wireless slates from Interwrite. It appears you can have about 7 of these active in a classroom at once. The teacher could have the master slate that overrides the rest, and students could pass them around. This would offer similar functuality to the Tablet PC at a much lower price, and the units are quite durable. The drawback is the learning curve--students would all have to learn how to use the slates. Again, it's not difficult, but it's awkward at first and you don't want your learning to run into roadblocks as students fumble with the slates.
I think that sums up my research. At this point I'm learning toward the wall-mounted Smartboard and projector with a single wireless slate to be used by the teacher. I can practice over the summer at my home computer which should allow for a smooth interaction with the Smartboard when school begins in the fall. My students are going to LOVE walking up to the front to write directly on the Smartboard and I think it will be a great way to involve those students who typically don't participate. So the non-responsive whiteboard doesn't appeal to me.