CSS, Still not there?
When CSS1 first reared it's ugly head in 1996, it was probably one of the most controversial changes in Web UI history. Over the years, we've all come to appreciate to some extent, the intended purpose of CSS. In most cases it does as intended and does it well. But, even after 9 years we're still up to our ears in browser incompatibilities, and until CSS 2 is fully adopted everywhere an un-intuitive way of creating tables in CSS. We all know how well floating divs works in CSS 1 *cough*. How can it take 9 years to replace (whatever you want to call it) a simple tag based language (HTML)?
Tables
All to often I've ran into the "Purist" movement, and been given the proverbial speech "Don't use <table>, you can do the exact same thing in CSS". Sure, after wasting half a week on ironing out browser incompatibilities and general CSS awkwardness you can do anything. But what these purists tend to forget is the age-old acronym K.I.S.S (keep it simple stupid). At the end of the day, it's about getting the job done on time and as "standards based" as reasonably possible. It isn't about following every recommendation or guideline to the letter, it's not realistic and is not a cost effective way of doing development. Read this fellas page for some more rants on CSS & Tables.
The future of Web UI
Delivering web based applications over the web is here to stay, and is going to continue to grow as traditionalists realize the benefits. The delivery method is the biggest hurdle, and hopefully over the years it will improve. Writing web software for several browsers is a chore, and there is no rhyme or reason for the issues web developers are faced with today. We need a solid, well-thought out, intuitive way to build applications that is written once and runs on any Browser (if that it is continued to named as such). Macromedia Flex, Open Laszlo and a few others are moves in the right direction, although they still rely on a plug-in and have some client performance related issues that need to improve. Hopefully in 5-10 years, the Web based application industry has the delivery model it needs.