Not entirly correct....
You need the SAPI runtimes only if you are on XP, or if you intend to use the L&H TTS3000 engines with the Microsoft Agent Genie, Merlin, Peedy and Robby characters (and possible other 3rd party characters). In other words, not everybody needs it.
Also, SAPI4 is not the same as SAPI5!! Engines made for SAPI4 will not work 100% with SAPI5 and vice versa... SAPI4 does things that SAPI5 doesn't and vice versa... eg: If an engine requires SAPI4, then install SAPI4 and not SAPI5 (of course you can install both if you like)....
Everything you need to know, etc... can be found on
http://www.microsoft.com/msagent/ (or on the links you'll find on that site)...
/ 
