One major weakness of the Windows Mobile platform, compared to S60 and the iPhone, is the rather poor Internet Explorer Mobile web browser. There are a few initiatives underway that may significantly improve that experience and if so, then something like the HTC Advantage could actually serve as my primary mobile computer.
The first new upcoming browser is being showed at DEMO this week and is called SkyFire. Dieter Bohn had a chance to see a demo of it in action via Skype and posted his thoughts. SkyFire is a server side browser so all of the heavy lifting is done on their servers and then sent to the user. Apparently, the browser supports full Flash and AJAX too so it may be a great solution. However, these server side solutions are not generally free and require a subscription model so you may need to balance out how important the full internet is for you.
A server side solution was started a few years ago and you may remember Bitstream's ThunderHawk. When I tried it out it did a good job of bringing the internet to mobile platforms, but had some clunky UI features and an awkward on-screen keyboard. I haven't checked it out for over a year and am not sure how much it has been improved since then, but it may be a good solution for you as well.
UPDATE: Ed Hardy posted a first-look review of SkyFire on Brighthand and it looks like a winner. I signed up to be considered for the beta and hope I get a chance to play with it soon too.