I wouldn't put too much stock in the results. Tr.im had that intentional downtime, but more importantly, ls.gd is down right now for me (may change later):

http://downforeveryoneorjustme.com/ls.gd

I'd stick with bit.ly or ow.ly. Also, there's u.nu, which has a nice gimmick if you really need shortness. It wasn't included in the results.