Just saw this thread so might as well chime in...

Thanks mrgsoft for support :)

As for AJAX support, it's been out there for about a month now I think via a tutorial on my site (mrgsoft has referenced it). It does work quite nice with it, and if you need AJAX support in pre.4.5 releases you can use it.

However... if you have a chance of using 4.5.0 it would be much smarter to use the native implementation of DNN. For a bunch of reasons... to name a few... support, framework integration, etc....

One thing you will find a cumberstone (not by the fault of DNN team) is that it's optional to have AJAX installed and used... this would mean your modules need to be prepared and have a fall back mechanism in case if AJAX is not present. DNN team has been good enough to provide you with the means to test this (is it enabled and does it exist), but you yourself need to make sure that your users don't suffer.

Nothing is needed on the client. AJAX is just normal server code, and normal javascript... packaged into a higher level of abstraction.

As for development, you have 3 options:

a) Write double code, one with AJAX, one without (you will start seeing the difference when you start writting components, using web services and such and when the code you need to write starts pilling) - and then you can use the logic which you've mentioned above

b) Make you module ONLY work with AJAX, then you add a dependency upon installation which will warn the person installing your module that you must have AJAX, and then add only AJAX support.

c) Don't use AJAX at all.

I belive the descision is case by case base, somewhere you will go one way, somewhere another.

P.S. Thanks  I appreciate comments like these, I like to know that my effort has payed off

Actually I don't know... must admit that I don't pay attention to that part simply because a whole lot of other things will not work if it's turned off (e.g. the most basic form of postbacks is done via a javascript function) that the fact that my code won't work will be the least problem to the end user.