I just switched from the Medtronic Minimed to the T:Slim X2 a couple months ago. It definitely takes getting used to, especially filling the cartridge, but like others have said, it’s not a big deal after you do it a couple times.
One of the big things that has annoyed me is the insulin waste. It doesn’t look like it wastes a lot, but compared to my Medtronic pump, it does. First, it takes about 20 units for the pump to “detect the cartridge.” So I was filling my Medtronic pump 130 units for 3 days, but I have to fill my Tandem pump 150 units. My nurse practitioner said that’s totally normal for the T:Slim.
Also, my Medtronic pump I could run all the way empty, so even when it said the reservoir was empty, I could keep using it until the tubing (which holds about 10 units) was also empty. The Tandem pump completely shuts down when the reservoir is at zero units, which I find especially annoying because it alarms (loudly!) every five minutes until I put in a new cartridge. So this means it wastes another 10 or so units that’s still in the tubing.
There are definitely pros to the T:Slim, including the relationship with Dexcom and the basal IQ technology. But I would consider the insulin waste a con.