Yes, but do the math on the ROI and be sure to allow for the delivery time until you can start mining. ASIC's as currently priced will never pay for themselves.
Recenlty I was considering to invest into GPU mining rig, but ended up with the same conclusion. it's not possible to get money back after invest. But powerful ASICs like Avalon or BFL still can generate some profit.
Difficulty increase history is following (
http://blockexplorer.com/q/nethash/2016):
Date Block Number Difficulty Difficulty increase Difficulty increase (%)
08.01.2013 215712 3249549,58 269 913 9,06%
23.01.2013 217728 2968775,33 -280 774 -8,64%
05.02.2013 219744 3275464,58 306 689 10,33%
18.02.2013 221760 3651011,63 375 547 11,47%
01.03.2013 223776 4367876,00 716 864 19,63%
14.03.2013 225792 4847647,15 479 771 10,98%
24.03.2013 227808 6695826,28 1 848 179 38,13%
05.04.2013 229824 7672999,92 977 174 14,59%
17.04.2013 231840 8974296,01 1 301 296 16,96%
30.04.2013 233856 10076292,88 1 101 997 12,28%
12.05.2013 235872 11187257,46 1 307 161 11,03%
25.05.2013 237888 12153411,70 1 307 161 8,64%
Last year average increase every two weeks was 3,74%. This year it is already 12,87%. And it will go up after all Avalons will be delivered. And then there will be bunch of DIY miners from Avalon chips, and probably BFL. Very soon mining will be profitable only for miners with rare elite hardware.