
When it was first released, I was very impressed. The momentum scrolling was great and there wasn’t much to dislike except the batteries. It chews through batteries like a high powered camera flash, and they die when you least expect it. Carrying batteries around is an annoyance that really should be confined to the Stone Age. The challenge with user replaceable batteries on items that go through a lot of batteries is that you need to carry them with you which adds bulk to your laptop bag, if you remember to switch them over after you’ve replaced them. Carrying a micro USB cable is a simple method and I’m really surprised that Apple haven’t incorporated rechargeable batteries in the keyboard and mouse.
The second issue I have encountered with my Magic Mouse is the consistent failure of the bluetooth in the device at about 18 months. I’ve generally been forced to replace my device every 18 months which I don’t see as a reasonable replacement period for a premium device that costs the better part of $100 when it was released. It starts with some intermittent bluetooth failing on the device and eventually it's happening so regularly you’re forced to throw in the towel through utter frustration.

After another the 3rd magic mouse failure, I moved to the Logitech Anywhere MX for two months which did the job, but I hated the attached USB plug. Whilst I loved the dark field, the scroll wheel was horrible coming from the touch mouse with momentum scrolling and I started looking for an alternative. That brings me to the T631 mouse which looks like a miniature version of an Apple Magic Mouse.

Logitech are producing some great devices these days and this is one of them. This mouse is about 2cm shorter than a Magic Mouse which may or may not be a good thing for you. It comes packaged in a nice plastic case (not usable for ongoing carry) with a set of instructions and a micro USB cable. You’ll need an internet connection for the latest drivers (not mandatory to make it work but the Logitech Preference Manager is required to enable gestures. A restart is required so don’t load up too many apps or you’ll have to shut them for the restart. After downloading the 58MB preference manager, you can install, restart and you’re on your way. Logitech give you a variety of preferences, which pretty much cover the entire spectrum of Apple gestures available on the Magic Mouse and a couple of extras.

From a quality perspective, the Logitech is close to the Magic Mouse but I prefer the Magic Mouse matt look rather than the Logitech look where it almost seems like there are machine marks on the aluminium. I don't believe the Logitech is necessarily sub standard compared to the Apple, but I think Apple has paid better attention to detail.

In use, the T631 is pretty much on a par with the Magic Mouse. The click is solid and familiar and I didn’t find any issues adapting to the change. Getting the preferences to my liking took a little way, largely because you get used to a particular level of scrolling and mouse speed and finding the same settings with another product takes a little getting used to. I did find that the mouse speeds are faster than the default Magic Mouse which saved me having to use some third party apps to increase the mouse speed. Apple have this perception that users are going to move their mouse slowly across the screen and don’t seem to want to give them the ability to reach any higher speeds.

The bluetooth connectivity was as simple as it gets. Open Bluetooth settings and connect to the device. One thing I really like with this is that the T631 allows for two devices with a small switch on the bottom so if you have more than one Mac device, you can use a single mouse for both of them. Whilst I don’t have more than one, I did like the flexibility offered by Logitech. It’s a simple and well thought out concept.
I was testing on Yosemite and some of the forums had led me to believe that mouse would only function as a normal mouse without some of the extra features, but all of them seemed to work fine for me. Maybe Logitech has released updates since this forum post, but on the public beta of Yosemite, I received no such issues although I have to admit I have not tested all gestures as they do not meet my personal preferences.
There isn't much you can say about a mouse other than does it connect, does it work, and how much flexility does it offer and it meets all of those. As you can

Looking at the things I don’t like, I don’t think they did true ergonomics testing on this mouse. It’s tiny and most would argue it’s too small. A lot of people battle with the Magic Mouse and this makes the Magic Mouse look like a brute. This means it does take quite a bit of getting used to and I’d still like to see it at least 1cm longer, maybe even 2cm. Whilst I understand its a laptop mouse, that doesn’t mean it has to be so small that it impacts ergonomics and if they released something larger with the same functionality, I’d probably buy it. My wife wasn't bothered by the size so this may be a personal issue.
The second thing is the cable which has a right angle at the end. This means it does not work with my scala rider motorcycle headset which means I won’t carry this cable and given most people use a cable for more than one device, I don't understand the need to have the right angle on the cable. You can't use it with the cable attached so there is not point.

Some people may be disappointed at the lack of cover, but I personally find them more of an annoyance than anything else.
In conclusion, this is a great little mouse and for users who are unhappy with the Magic Mouse, it's worth having a look. Logitech list the retail at $99 but if you look around, you'll find it for under $90. It doesn't come cheap, but it's a premium level product.

Pros
Bluetooth - Always good to have to use another port
Customisation - Provides a fair amount of flexibility to meet most requirements
Multi Device - Caters for two Mac (or windows devices)
Portability - Small which some users will appreciate
Rechargeable - Save on the cost of batteries or carry extra weight in your bag
Cons
Size - Its too small for my personal preference
Cost - Its $90 on special which is still expensive
Cable - Not the greatest rechargable cable design