The final outcome is a quick interface, as the amount of data exchanged between the web browser and web server is greatly condensed. Web server processing time is also saved, since much of it is done on the client. Ajax is more a natural progression from an existing set of techniques as opposed to being something completely brand new. Yet within that progression, things are markedly different than in previous years in a couple of key areas.
Ajax provides a device to juggle up xml with xhtml. It drastically abridges the job fetching things from the server. It also defeats some speed glitches that conventional Web development has fallen prey too. In most instances an Ajax based site will load quicker than a comparable traditional Web site. Ajax significantly reduces initial load times. Ajax has some problems that it needs to overcome as it continues to mature.
But it is a promising field to be involved within and as the years roll on, it probably will greatly affect the way we think about building Web pages and Web applications. It also has to be apparent that Ajax is not a technology as such but to a certain extent is a technique that merges well with other technologies and techniques. For example: XHTML XML, DHTML and CSS.
Actually, Ajax actually is DHTML with the xmlhttprequest object thrown in. It is wonderful to believe how one object can modify the whole scenario of web technologies.