I used to have both a Wodent Wheel and a Silent Spinner in my rat cage – I have a wheel addict in my group, so two wheels are needed for the others to be able to go for a run too. I was getting sick of the noisiness of the Wodent Wheel and the difficulty in cleaning it, as you can't even give it a quick wipe down without taking it apart. Having heard lots of good reviews of Tic Tac wheels, and having heard of a recent drop in the build quality of Silent Spinners, I decided to try a Tic Tac.
I first ordered a 16" blue metal Tic Tac wheel, as I had been assured by another rat keeper that it wasn't too heavy for even small rats to use, and I wanted to get the biggest wheel that would fit in my SRS. It took my rats a few days to get used to it: it's heavier than plastic wheels, but the bearings are much smoother, so it takes more force to get it going, but once it's going it spins much more easily. At first my rats seemed so unsure about it that I was worried they didn't like it, but once they got the hang of it, they really took to it. They loved it so much that nobody wanted use the Silent Spinner anymore, and there were arguments over who got to go in the "good" wheel.
So I got another Tic Tac wheel, a 14" blue metal one this time to conserve on cage space a bit. Both wheels are greatly enjoyed by my girls; I think there may be a slight preference for the 16", but they love running in the 14" too. It's been especially rewarding to see my largest girl, who previously would only go for a gentle stroll in a Wodent Wheel or Silent Spinner, actually go for a proper run in a Tic Tac. I think this is due to both the smoothness of the bearings, and also the size of the wheel: they all look more comfortable in even a 14" over a 12".
The one downside of the Tic Tac is that it is a bit fiddly to attach to the cage. At first I tried to attach it as one piece, which was a struggle, but on seeing ami_j's review above I realised that of course I could detach the metal cross-pieces from the wheel, attach them to the cage first, and then attach the rest of the wheel to the cross-pieces. That was much easier, but still fiddly. Combined with the fact that you're not supposed to get the bearings wet, this is very much a wheel to clean in situ. Doing so is very easy however: I just give it quick wipe and it's ready to go. Unlike the Wodent Wheel and the Silent Spinner, there are no annoying gaps for dirt to get trapped in. There is a welding join at one point across the running track, and also between the back of the wheel and the track (apparently the non-coloured wheels don't have these joins?); dirt can accumulate here, but it's very easy to clean out.
I've read that the large central bolt that attaches the wheel to the cage doesn't fit through narrow bar spacings: the central bolt on my wheels measures approximately 7mm across. It fits through my SRS bars without difficulty, but I forgot to test it on my Freddy 2, and now that it's been attached to the SRS I don't want to detach it again to test.
There is also the option to buy the wheel attached to a metal stand, so it can be freestanding. I asked the seller if the wheels sold with the stand could be detached from the stand and attached directly to the cage (to give me flexibility in wheel placement); they said that the wheel with the stand doesn't normally come with the cross-pieces that are needed to attach it to the cage, but if I sent them an email when I ordered one, they would include the cross-pieces for me free of charge. They also included instructions on how to swap the stand for the cross-pieces; it was very easy to do and only required an adjustable spanner.
Overall I would happily recommend metal Tic Tac wheels, provided you can clean it in situ. I would also recommend the largest one you have the cage space for: the difference between a 14" and a 12" is already pretty great, but my girls look most comfortable in the 16".
5/5, would buy another one if I had another cage!