Particularly valuable if you don't have a flat rate data plan or if you are roaming, WiFi is supremely useful but - undoubtedly - something of a nightmare to use.
Case in point: When I was away on business recently my wife and daughter were on holiday in sunnier climes. My wife wanted to keep in touch with her mail etc. while she was away and she didn't want to spend a fortune on GPRS, so WiFi was an ideal solution. She uses a Touch Dual normally (non WiFi!) so I gave here an Eten X600 to take with her too (also handily loaded with navigation software for the hire car!) That was the easy part, the tricky part was explaining the intricacies and oddities of WinMo connection manager, all the different places the setup and settings live and so on. She's very Windows Mobile savvy, but it just is an AWFUL experience.
At it's heart, WeFi eases this pain. It provides a single UI for turning WiFi on and off, discovering networks, determining which networks have internet access and automagically connect to the best one at any given time. It's a brilliant concept, and it works great... i've been testing it on my Pocket PC, my Mac and my WiFi's Vista laptop even!
WeFi also has some interesting social networking features built in, but I think the real gem for us Windows Mobile users is the simple connection management ability.
So it's still useful, it's still free, and now supports more platforms than ever. Grab it from the Android Market.