I prefer to work in Midi rather than ABC and Cakewalk is my favourite program. If you wish to consider that type of software, Cubase is another program worth considering.I don't know what you are looking to do but Midi and ABC are desinged with differen aims. If you are looking to produce musical notation, ABC is superior to Midi. On the other hand, If you are looking to get maximum control over your soundcard (or other Midi devices), add effects etc, Midi is the best option.
I haven't found any one program that meets all my reqiurements but I work in Midi and if I want to produce notation, I often convert the Midi to ABC (Midi can't even handle a repeat section as notation) and make the necessary changes.
I use a variety of shareware ABC programs and I have yet to find one that is 100% reliable in converting between these formats. Probably the most useful ABC program that I use it Melody Assistant which is $15 sharware, provides a graphical interface, can handle a nubmer of file formats including Midi and ABC and is available for PC and Mac.
I am not aware of any "high end" ABC programs but it might be worth your while looking at more shareware options. The best starting point is http://www.gre.ac.uk/~c.walshaw/abc/.
Also, depending on your requirements there are other shareware programs such as Noteworthy composer which I don't think handles ABC but will read Midi that may suit your needs.
Currently, to handle all the fomats I use, convert, diplay as .gif etc, I am using: Cakewalk 3, Mid2Abc (a program somebody is currently devoloping which apart from converting has a text based editor), ABC2PS, GhostView, Melody Assistant, Noteworthy Composer, Mozart and Mid2Txt (for Mudcat although Alan of Australia has kindly provided some web space for midi files and this program may become redundant in time). It gets confusing at times but I seem to have uses for all of these.
Jon