Well, FR24 has very recently updated the format of its website, and I can't say I'm impressed with what I've seen so far...
At first it was all fine. The display looks a lot smarter, scrolling through the airport arrival/departure boards and selecting flights to track was a lot smoother. One minor quibble is that the new site only displays some flight data, like aircraft altitude and ground speed, for free. The old site, used to display other data like the aircraft's latitude and longitude, squawk, radar, and vertical speed (rate of ascent or descent). Now it appears these other data are behind a paywall.
However, after a few days using the new format (I use an iPad mini), I've come across multiple problems, none of which were there at first. The mobile website has started repeatedly crashing. The old version had its fair share of crashes, but nowhere like as often as the new version. The webpage automatically reloads after a crash, but I've found that after a crash the new version doesn't reload airport flight lists or even display aircraft on the map, meaning you have to close the tab and open a new one.
I found the most common cause of crashes on the old version was scrolling through lists or panning maps too fast, or trying to click on other flights when one flight was still loading, but now even doing nothing can cause a crash on the new version.
In addition, the airport flight lists don't show all the airlines' names. Some airlines only have their IATA code displayed, which looks like this:
Flight Airline
LH956 Lufthansa
ZB446 ZB
BE411 Flybe
FR1122 FR
Finally, last time I visited the website it wasn't even loading a photo of any aircraft I clicked on. I'm not willing to fork out money just to have a website that works properly—that should be the bare minimum requirement for any website, so I hope very much that this is a work in progress and these are only teething problems.