The upcoming releases of ffmpeg and curl will both have support for rtmpdump's librtmp. As such, people writing scripts/tools built around rtmpdump may prefer to use those other programs instead.
curl is already used ubiquitously in scripts that automate downloading thru various protocols. Likewise, libcurl is used in a lot of software for the same purpose. As a straight download tool, it may be preferable to use something generic like curl instead of rtmpdump.
The ffmpeg software suite handles all kinds of media formats and protocols. If you're looking for an all-in-one program that handles rtmp, rtsp, mms, etc., I think ffmpeg is a good choice. A lot of tools built around rtmpdump already use ffmpeg to transcode the download videos into other formats. With librtmp integrated into ffmpeg, you can do everything in one shot instead of needing to run rtmpdump first followed by ffmpeg.
Also, in a lot of cases the only reason you're downloading a stream is so that you can then watch it in a better player than the CPU-hungry Adobe junk. In that case, with ffplay you can simply play the rtmp stream instead of having to download the file at all. (Also mplayer can do the same.) Using ffplay or mplayer to play the stream directly in realtime may be more convenient when your network connection is fast enough to pull the media down without stuttering. Also, ffplay fully supports the Seeking code in librtmp, so you can seek forward or backward to arbitrary points in the stream while you watch.
Check out
http://ffmpeg.org/ for ffmpeg,
http://curl.haxx.se/ for curl, and
http://www.mplayerhq.hu/ for mplayer. All of these packages are highly portable and available for most operating systems / CPU types. ffplay and mplayer both support hardware-accelerated video decoding, so they tend to be much more efficient than anything Adobe can produce, and don't have any of the security holes that always accompany Adobe software.