If you are from a background of programming from your education and/or your working experience and want to switch over, SAP ABAP is a good choice. If you approach and follow it correctly, you may become the specialist of an area. We will discus it a little later.But if you have, say, more than 4-5 years of experience in some other technology or programming language, you must weigh the pros and cons carefully. First of all, you won't get much credit for previous experience, if you make a switch. That is because changing to SAP ABAP is not an extension of your previous expertise. It is a different language and works in a different environment. It may be better for you to proceed in the same technology or an allied technology where you can maintain your edge and get due credit.
Another factor which you should consider is – ABAP is a platform specific and proprietary language. If you love the freedom in which languages like Java can be used on multiple platforms or even others like C++, ruby, etc. to develop independent applications and to do other fun geeky stuff, ABAP may not be that stimulating.
It is primarily because it is a business language. It can only be used on SAP platform for solving business problems – customize SAP software as per customer's business requirements. If you are okay with that, you will not find it damn boring either. It's a different kind of fun altogether to understand and support real-life business processes. If you find it interesting, you can have a satisfying career.
Now there are two way of advancing in SAP ABAP career:
(1) Generalize, or commonly called General ABAP, where you do programming for whatever application (SD, MM, Fi, PP, etc.) you get work,
(2) Specialize in a specific application rather than generalize across different modules. For example, an ABAP developer working in HR module and sticking to it over years acquires specialized skill in that module and the can keep her/himself updated on the latest developments and enhancements like ESS, MSS, E-recruitment, etc. If s/he is paying attention to and understands the HR business processes also, s/he becomes the techno-functional consultant, as the terminology goes in SAP circles of the module. Such a consultant is always sought for specialized work because of the experience and expertise involved.
Best Wishes for a wonderful career !