The thing I've noticed with the last two or three updates is that you lose the diving alarm on the subs.
Otherwise, I just installed RA 1.51 last night and I'm still tweaking some little things. "Marvin The Martian" is going to shore duty on the Seawolf and Virginia class boats.
I did have one "ctd" last night while I was paging through the USNI database entries but that happened right after I did the 1.51 install. Otherwise, its too early to start listing any bugs.