On the sites that use AJAX correctly and effectively, I must admit that the UI is a marked improvement over past technologies. In many cases, though, it can be overkill: a waste of bandwidth and programmer time (i.e. it would be unnecessary for the Google home page to use AJAX to display search results). As an occasional Lynx user, I really appreciate when a site keeps alternate browsers in mind.
That said, I agree with jw that catering to users of ancient, insecure browsers is probably a waste of time and a barrier to progress. I disagree with a strict cost-benefit approach, however. As an analogy, Microsoft has been benefiting from this phenomenon for years due to hardware companies who only write Windows drivers, while NVidia is a good example of a hardware company which provides open source drivers and receives loyalty and sales opportunities because of it. Additionally, supporting cell phone users and the visually impaired is certainly a good idea, even if only a small percentage of visitors fall into these categories.
Of course, as numerous others mentioned, it's important to be aware of your target audience, but don't be surprised if your actual audience does not necessarily match the one you have in mind.
That said, I agree with jw that catering to users of ancient, insecure browsers is probably a waste of time and a barrier to progress. I disagree with a strict cost-benefit approach, however. As an analogy, Microsoft has been benefiting from this phenomenon for years due to hardware companies who only write Windows drivers, while NVidia is a good example of a hardware company which provides open source drivers and receives loyalty and sales opportunities because of it. Additionally, supporting cell phone users and the visually impaired is certainly a good idea, even if only a small percentage of visitors fall into these categories.
Of course, as numerous others mentioned, it's important to be aware of your target audience, but don't be surprised if your actual audience does not necessarily match the one you have in mind.