I took an hour or so to go through the RT bug list of known Rakudo issues, searching for things that I think should be fixed by April. Here they are.
There are currently over 400 new/open bugs in RT. These only form a slice of those. My criteria for slicing have been, more or less, "what would hurt more, fixing this bug, or having to explain to the hordes of new users in Q2 2010 why this particular bug exists?". Whenever the latter weighs heavier, I include the ticket in the list.
(This also shows a different statistic, and quite a positive one: while there are many bugs in RT right now, many of them pertain to corner cases, or minor issues. In other words, Rakudo is getting more usable.)
For those in a hurry, I've marked the most egregious issue in each category in bold.
On the command line, Rakudo...
During parsing, Rakudo...
At runtime, Rakudo...
Perhaps the most subjective part of my list. What finally made it on this list are features which are "almost there", and which people will probably ask about if they're not fully implemented.