Sciral is an interesting concept.  Here are some ideas you may want to consider:

(1) Organize the dates on the top of a list horizontally something like:

Year-----------------------------------------------------------------------------...
Month------------------------------------------------------------Month---------...
S M T W T F S S M T W T F S S M T W T F S S M T W T F S S M T W T F S..

(2) Select by week, month, year.

(3) Zoom into a particular week or month.

(4) Change the starting date of a task (maybe I missed this).

(5) Consider the word "Activity" instead of task.

(6) Assign time or work units to each task.

(7) Show a summary histogram or number per day that rolls up time/work units to see how much is scheduled to be done on a particular day.

( When completing a task, ask if you want to restart the sequence on that day.  It looks like it does this automatically, but that may not be what you want.

(9) Rather than think of a task having a range consisting of only two numbers (min and max), think of its range as three numbers: optimal interval (e.g. 14 days), acceptable minimum interval (e.g. 10 days), and acceptable maximum interval (e.g. 16 days).

(10) Printing.

(11) Exporting/syncing in some way with iCal.

(12) Today zoom-in showing what is late, what is due today, what is coming up, how much work is due today.

(13) When a new task is created, it looks like Sciral assume the sequence should start today.  That's not always the case.  For example, today is Monday but I'd like to create a task that should occur every Saturday.  That leads to another thought -- you may want to expand on the ways in which ranges may be entered.  For instance, "every other Saturday minus 2 days and plus 3 days".

Peace,
weeb