Currently, there is some talk in my university concerning a change in our lecture rooms from blackboards to smartboards (or other alternatives, such as a smart podium). For that reason, I'm interested in the following:

1. Do you have experience in teaching math using smartboards, as opposed to blackboards? Good/bad/...
2. Do you have (second-hand) experience in teaching non-math courses using smartboards?
3. Is the size of the group of students relevant for deciding to upgrade to smartboards?
4. What is the general preference of students in this matter?
5. Are there interesting alternatives (other than blackboards or smartboards)? Also alternatives which do not yet exist may be posted, if reasonably feasible.

I decided to post the question here, as I can imagine that similar discussions are being held at other institutions (and the outcome may have a profound influence on how we teach math in the near or distant future).

[Some more background: the specific lecture room we are talking about at my university has a capacity of 450 students; it is currently equipped with 9 big black boards (in rows of 3), all of which can be shown simultaneously as the room is quite high. There is also a beamer which can be used if one lowers the 3 blackboards in the middle, leaving 6 others for simultaneous use with the beamer. A typical course in this room is for 250 up to 450 engineering students - so not for mathematicians]