I gave this phone a glowing review when I first got it, but since then have discovered a big flaw in its ability to run a range of apps - see 'UPDATE' below.
The Wildfire S is quite a deal. Even after buying a 32GB Micro SD card, it works out cheaper than the latest 32GB iPod Touch, yet it has the features of an iPhone costing over twice that (including GPS and, of course, the ability to make calls). It's outclassed in some respects (such as performance) by the Apple products, but it still does the same things, and the Android operating system is beginning to rival Apple's platform for ease of use and choice of Apps.
The Wildfire S is smaller than an iPod/iPhone, and in my view more useable as a phone for that reason. The screen is smaller than Apple's, although the area below the screen is also a touchpad, with four standard 'buttons' (Home, Menu, Back and Search) which make using Apps more consistent. Performance is fine - you'd need to be a hard-core gamer or 'milliseconds are money' business user to find it insufficient. Battery life is, as many have said, poor - literally 5-6 hours if you use all the toys - but if you switch off mobile networking and GPS (easy to do) it's much better, so the choice is yours. On the upside it charges very quickly.
The phone's version of the Android operating system comes with HTC's own user interface ('HTC Sense'), which does, indeed make sense - it's easy to find all your apps, and fairly easy to get to the settings you need. The touch screen is as responsive as Apple's, and although the on-screen 'keyboard' for typing is a bit cramped, I don't think it's any worse than the iPod's. The Adroid Marketplace is, if anything, less hassle than Apple's, and there are plenty of apps - within hours I had my Wildfire equipped with (free) apps to do all those iPhoneish things like read barcodes, search by image (Google Goggles) and even find tunes by listening to you hum them (the amazing SoundHog). Satnav software is included and actually works, for walking around streets as well as driving.
Anyone who's waited what seems like all day for iTunes to sync their iPod/Phone will be pleased to hear that you can treat the Wildfire as a disk drive and just copy music etc across, although there is an HTC sync app if you want it. Sound quality is slightly worse than my 3rd-gen iPod Touch, as is video quality (it doesn't always quite keep up during playback, but that's what you pay for with Apple). The 5MP camera has a very effective flash and takes a pretty good pic, although pressing the touch-screen button while holding it is difficult. 720p video suffers badly from 'jelly-roll' when panning, but again this is what you get for this price.
The Wildfire S is a very likeable product, and excellent value for money. It feels well made, works well and has masses of functionality, and if on occasions it isn't as smooth as Apple's alternatives, that's more than outweighed by the savings. It makes sense even if you don't get a calling plan (so can't use mobile networking), but for just a few pounds a month (or even on Pay As You Go) you can get a 'SIM Only' deal that will turn it into a full-scale iPhone alternative.
I've found that if you like installing a variety of apps, then the Wildfire S has a problem. All apps (even ones that have been 'moved to the SD card') take up space on the phone's internal memory. The Wildfire S only has 150MB of that available (out of 500MB total), and it soon gets used up (it's used to store contact information and temporary data storage too), so however much space you have on your SD card, you can't install any more apps. The need to use internal memory applies to all Android phones, but presumably HTC's more expensive models have more internal memory (although I'd check before buying). For me, having a range of apps installed is part of the fun of these things (I even used my iPod spirit level app recently!), and this relegates the Wildfire S from iPhone alternative to camera phone with moderate app capabillity. Shame.