Yes, I’m in two dynasty leagues on that site - one just entering year 2, and one that has just had its start up draft over the last week or so. I would agree that the site offers a huge amount of customisation options - in terms of drafting, scoring, fixtures, and even having your own colour scheme and look-and-feel for your league’s web pages.
The flip side of all the customisation is that there can be a lot of work for the commissioner to do to set up and maintain the league, so you need to be sure you have a good set of players to make it worth the effort! Also, the site isn’t free, though a charge of about £5 per player per season shouldn’t put anyone off.
In case you are interested, I am setting up a money league with multi year player contracts, which will start with a live draft day in a pub in Southampton in May. It is advertised on this site here : CANCELLED - Bargate Bowl fantasy league 2016 - let me know if you are interested as there are still spots open.
I am expecting to run the league off-line during the off season, and on the NFL’s own fantasy website in season. But there would be scope to move it to myfantasyleague if the players were keen - as you say, it gives lots of options like draft pick trading, which I will be organising on a spreadsheet for the time being!