The Icom IC-751A is a very competent transceiver with good signal handling capability combined with with good selective filtering. Only drawback might be the lack of some of the bells and whistles common on modern transceivers, and a slightly high phase noise (though not as bad as on the Drake TR7/R7.)
Some very good test data may be seen at the site of Tom Rauch, W8JI, http://www.w8ji.com/receiver_tests.htm. Rob Sherwood, NC0B, has also done some test, see http://www.sherweng.com/table.html (note that the tested transceiver here is the IC-751, i.e. not the A-model that include some improvements.)
More information about Icom equipment can be found at http://www.ab4oj.com/icom/main.html and http://www.classicicom.com/
For computer control you need the Icom UX-14 board, or even better, and easier to come by, the Piexx UX-14 clone named UX-14px, http://www.piexx.com/index.php?main_page=product_info&cPath=7&products_id=19. As the Icom UX-14 is very hard to come by, I bought the Piexx variant. One added bonus on the Piexx board is that you get S-meters readings which is very handy. You also get a PTT line that is controllable via the CI-V buss.
Program-wise I am using the hamlib library and associated command line commands, http://hamlib.sourceforge.net/, and as graphical user interface I am at the moment using grig (Gnome-rig), http://groundstation.sourceforge.net/?grig.
I have gone through the hamlib ic751.c file and added some things missing, so that the hamlib interface for the IC-751/IC-751A should now be more or less complete. The new code went into hamlib version 1.2.5.
I had problems using grig-version 0.4.3, so I am now using 0.5.csv which seem to work for my use.
Some problem areas exist. Especially the trimmer capacitors (VCT51 family) used in the VCO circuitry (these trimmers are also used in the USB part of the BFO and in the RTTY/CW transmit circuitry.) For information about some of the problems, and their cures, see http://www.icomamerica.com/support/kb/Default.aspx
I have identified the following bad (they only go bad if they are contaminated with wax) trimmer capacitors:
There are some modifications around. Some are listed at http://mods.dk/index.php?ModelId=292&RadioRec=icom