Of all the forumites here, I'm probably your man (or Dwarf) when you want to talk about Dispossessed. As
@Warden says I do have some Fyreslayers (only 10 Vulkites at this point but I'm intending to expand upon this to create a 1000 point army at least by next year), but the vast majority of Dwarfs I have are fantasy Dwarfs, or in AoS, Dispossessed. Regular Dwarfs were my first army and I still attend to my army regularly (bought an Ironbreakers box today in fact). I did have a look at their rules and allegiance abilities in AoS and while they aren't the best army at this point in time, they are still competent thanks to the General's Handbook allegiance abilities. Their Runelords, for example, are exceptionally useful as they can unbind a spell each turn as if they were wizards. The allegiance abilities do a great job of capturing Dwarfs' exceptional bravery too in that if they fail a Battleshock test they can roll a dice and treat it as being passed on I think a 4+. They are also the most well-armoured of the Dwarf factions, definitely more so than Kharadron and they generally have better armour saves than Fyreslayers. Furthermore, they can ally with Fyreslayers and Kharadron (in a Dwarf ally triangle) so that they can make use of Kharadron airships and Fyreslayer Magmadroths if necessary. This also works in reverse in that Fyreslayers and Kharadron can use Dispossessed units as allies to fill in their own weaknesses (certainly I have included my Runelord as an allied unit in my Fyreslayer list to give me that anti-magic boost).
However, they do have their disadvantages. As
@Chico says they are by far the slowest of the three Dwarf factions - Kharadron can zoom along in their airships and Fyreslayers, while having slow basic troops, have fast Magmadroths and can deep strike some of their troops using Runesmiters. Dispossessed can do the latter if they use the Ancestral Pickaxe artefact, but it only applies to one unit of your choice now that Miners aren't part of the army. They also lost all their artillery that made them so devastating in 8th Edition, with the Bolt Thrower and Grudge Thrower being scrapped entirely and the rest going over to Ironweld Arsenal. They can still use these machines through allies but can't take them as if they were part of their army (which is stupid if I say so myself as they've been part of the Dwarf list for so long). Furthermore, because they don't have any really big stuff, Dispossessed are now the Dwarf faction that is most reminiscent of a horde army, which is the opposite of what they were in Fantasy.
Nevertheless, you can still run a good army if you try to focus on killing the enemy rather than specifically capturing objectives (which you are not going to be able to do unless you bring Kharadron or Fyreslayer allies). To do this I certainly recommend at least one or two Runelords and a Warden King as your general (as he can trump most other enemy infantry characters), and otherwise choose whatever units you want, as the one good thing with Dispossessed is that practically all of their units are competent at the moment.