In reply to Derry:
Several times in several areas.
It's very different to Kyrgyzstan. Far less western influence, more regional influence. Like Kyrgyzstan it's split in two halves, though east-west rather than north-south, so most mountain areas you are accessing from the southern and western sides of the Pamir-Tien shan knot work and weather goes with that, including Asian monsoon influence that can affect river heights. Depends totally on where you are and when, the Alay Chu/Fergana has a different weather pattern to the Badakshan side of the country.
Dushanbe is a much nicer city than Bishkek, though rapidly being overhauled. Regarding Dushanbe's markets, perhaps a bit less Chinese/Turkish and more Russian, though Tajik food is less Russian than the culinary purgatory Kyrgyzstan can be, the Persian/Afghan influence is stronger. The western tourism industry is less represented so less of the fake gear you get in Bishkek and Osh. I used gasoline stoves when there so never looked for canisters. Make sure you have everything when you leave Dushanbe as even Khorog is a big step sideways.
The general infrastructure for getting about is less in place than Kyrgyzstan, the country is poorer and more topographically convoluted, but what is there works well though is bumpy. Roads beyond Khorog are being upgraded as they connect more to China so trips out into GBAO are not the ordeal they once were. The Aga Khan funds tourism development programs thru PECTA with home stays and transport which is your best bet for getting around and keeps what little income comes to GBAO in the area.
Visas and permits these days are easy to get and get the GBAO permit with your visa. Dushanbe can be painful for getting bureaucracy done in.
Mountain-wise, the Pamir is significantly less organized and accessible than Kyrgyzstan when you're away from the big ticket areas that have Soviet-style seasonal infrastructure. People live further into the mountains, not unlike Pakistan, with villages up valleys and small roads to them. PECTA is your friend here as local knowledge vital. They may be able to arrange gas canisters even.
Overall, Tajikistan is not straightforward to get to so make sure you have your back end planning in order, especially in the post COVID era. It was disjointed enough before and you cant just pop over into China or Kazakhstan. A friend was needing assistance in Dushanbe a year or so ago and the process of getting out on short notice was harder than most places.
It's a cool place and being somewhat overlooked has been it's advantage. Step carefully with some things as the effects of recent history are everywhere and not far beneath the surface. I keep mentioning the Aga Khan as that's a great organization to approach from and genuinely makes a positive impact, something you don't always see in the ex-Soviet states.