A web interface, though important to have, is a pretty sad substitute for a dedicated graphical interface system, so you will tend to need some amount of graphical oomph to get high quality interfaces.
Not to go too far off topic (I'd be happy to discuss it elsewhere), but while I have beleived similarly in the past, recent developments have really changed my opinion.
In partciular, with the extensive use of AJAX and DHTML and good graphic design, I've recently witnessed web interfaces that competed at the same level a dedicated, well crafted GUI. Very responsive (no press submit and wait page refreshes -- in fact, virtually no page refreshes at all), fully animated (panels appear and disappear -- sliding in and out, fading in and out, "exploding" out, etc very smoothly) and highly responsive (things change as soon as they are touched and automatically update as the underlying data changes -- i.e. a light level slider control will auto-adjust the displayed values and thumb location when a user somewhere else in the house changes the light level -- no delay on the web page at all). In this case, the company had hired a graphic artists to create some incredibly sharp control graphics as well, giving this a really "top shelf" look AND feel.
I've been pretty skeptical of Web UIs for use for more highly interactive and/or rich interfaces, but what I've seen has changed that. I saw a no-compromise user interface that could run on any platform and keep all the "heavy lifting" on the server, allowing for lightweight clients (as well as remote access and such). Further, because everything came from HTML source, tailoring the interface was remarkably easy.
This particular app was a touch screen interface and they used Opera as the browser because it has a "kiosk" mode that runs in fullscreen mode and hides all the menu bars, navigation buttons, URL fields and other things that look like a browser. The result was indistinguishable from a GUI based touch screen app -- there was nothing that would clue you in this was a web program from looking at or working with it.
As a result, I really do feel you can now have a sexy, no compromise interface via a web browser. I'm not saying the age of the GUI is over -- it isn't. Some things -- especially things that run entirely locally (like a word processor) I have a hard time seeing working like this (then again, I could be wrong). But for client/server type things, it is a reality now.
Gerry