There didn't seem to be much of interest for me this time around (other than 2 which were a no brainer) but having looked a bit deeper there's actually quite a few which have caught my eye now.
- Mushishi Zoku Shou
If you're not going to be picking anything else up this season (or very little), and haven't seen the first series of this already I'd highly recommend watching that along with the special asap so you can pick this (second season) up. Mushi was and still is one of the best pieces of anime I've had the pleasure of seeing so I fully expect S2 to be a must watch. Starts April 5th.
- Ping Pong The Animation
Likewise with the above, this is likely to be the other "must watch" show of spring. Or at least I anticipate it to be heh. Masaaki Yuasa. Starts April 11th.
- I expect this is something Anny will be greatly interested in too as Yuasa did the amazing The Tatami Galaxy, Kaiba too though I don't believe you've seen that.
Other possibilities for later:
Which shows will you guys be following?