Just browsing the pages and noticing that there are quite a few models which do not have reviews so I'll try to fill in some gaps where there are none.
This Ericsson T66 was released ages ago - some 7 years now in fact. I paid an eye-watering £200 for one at the time which was considered a bargain.
The first thing that will strike you about the handset is how incredibly small it is. The picture does not do it justice, really - at under 60 grams it is under half the weight of today's phones like the N95. It is tiny, yet in my own opinion, very nice to look at - better than Sony Ericsson's similar model, the T600. If I brought this phone out today, it would still get the 'wow' treatment and that's probably good testament to it.
With the probably exception of some Panasonic and Xelibri handsets, this is one of the smallest going. It's fairly unlikely we are heading back that way again. In the late nineties, the original 'brick' mobile phones led to manufacturers obsessing about the dimensions of their handsets, leading to a mindset of size (or lack of it) was everything. Handsets got smaller and smaller, until it was realised that colour screens, cameras, and MP3 players didn't function that well on small phones and a medium was restored.
Usage-wise the phone is good. Despite the small form factor, it's easy to use; reception is good, and the keypad is rather nicely designed, the seperate keys making it slightly easier to press each key individually, no problems there. I did not note any particular problems with sound quality or reception (although the latter may be network and location dependent).
All standard features are there, and nothing else besides. If you're looking to text and talk, that's fine - but nothing else.
The phone uses a mono screen - presumably to conserve battery life. But this does not hide the fact that there are several features missing that could have been included. The menu system with icons (present in many Sony Ericsson handsets of this era) missing, making navigation slightly more tricky. Connectivity issues - I can accept Bluetooth being missing (no real requirement given the no multimedia capability) but infra-red would have been nice. It's not here.
Disappointingly for me, the battery life was quite relatively poor for a mono model. Yes, in the older days, phones had to be charged more, but the life paled in comparison against models such as the Nokia 3510, or 8210. A one-hour phone call would easy put a big dent in the battery bar.
Build quality, for such a nice phone was pretty poor - and mine picked up faults after the 6-month mark with repeated faults with the keypad. This is not an uncommon problem, I have read and I ended up selling it.
It exasperated me at the time, but now having written this I can see how the sheer size of the phone leads to a trade-off in certain aspects of functionality and possibly Sony Ericsson were pushing the boundaries at that time and so build quality was probably not quite up there.
These are extremely rare nowadays - a working one especially and one would probably set you back around £30, still a good deal if you only want to use it infrequently. For me, the design was great but let down by the reliability and battery issues. Sony Ericsson seemed to agree and this style of design was dropped from the T-series in favour of a more multimedia-based approach.