I'm getting on really well with my new phone - the Orange M3100 I mentioned earlier this week. I won't bore you with the details.
One noteworthy point is that the device has support for WiFi - this was a deciding factor in my choice of device. Being able to browse with WPA authenticated access and even remote desktop into my home network is nice. The speed benefit of WiFi over GPRS makes the experience really good. The cost benefit of using WiFi instead of 3G helps too. The device switches traffic to the fastest available network out of WiFi, 3G and GPRS. All sounds good so far...
Being interested in security I've hit a snag that perhaps won't worry most people - there isn't a built in firewall on my phone. I know that there are several 3rd parties who provide personal firewalls for PDAs but the omission of built-in protection is disappointing. This limitation is not specific to the M3100 of course but rather to the platform itself.
The Windows Mobile platform includes a wealth of sophisticated security features including the facility for a remote administrator to erase it's data store if it's lost or stolen.
Given the extensive features for accessing and manipulating personally identifiable information (including email, diary and contacts) I suggest that a personal firewall should be installed BEFORE using WiFi.