It's becoming much more common than it used to be, probably as today's latest models developed for FTR are very stable indeed. The SEB JoyPod is a good example and increasingly seen in GB F-Class, mostly FTR but also a surprising number of Open shooters too. (Often the joystick bit isn't used except in initial set-up, the mechanism adjusted to give high-friction, and nearly locked up.)
Much depends on the firing line material / surface. In the UK, we shoot almost exclusively off grass turf and a good bipod handles very well on this surface. As pods have become ever wider and more stable, they cope with torque better, so the range of cartridges they can handle increases. I've seen people use 284 and 7mm Shehane rifles very well with bipods. Nevertheless, their greatest attraction is still to people using lighter recoiling numbers such as the smaller 6.5s and sixes.
Why use a bipod and not a good joystick front-rest such as the SEB Neo, Farley, and Dolphin Gun Co. models? Apart from the obvious one of price up front, there is the straightforward matter of firing line access and carrying the gear. I shoot regularly in a high hillside range where most firing lines are built on the hillside and tiered down it in a series of steps. The minimum distance to carry gear is 25-100 yards depending on how good a car parking spot one gets on arrival, but some distances involve much longer carries and for 300 yard comps involves a
very steep climb up a hillside on a path that is often wet with poor footing and buffeted by wind. I never take a front-rest to this firing line now, and use a bipod as matter of course as do many others as I'm exhausted carrying my Neo up the hill. In matches where winning scores are normally in the 99 / 100 range (199/200 in US scoring) with V (X)-counts in the mid teens, the absence of a bipod doesn't appear to be hampering people.
We also have a very interesting prototype super-wide and very light carbon fibre legs bipod in the system from Evo Leisure in the UK which I hope goes into production. It's already available in a pretty wide standard form, but the company made an extra-wide one-off and it is being trialled this season in GB national and international FTR by Stuart Anselm. I'd be very interested in trying on an Open rifle too. This link is to a Target Shooter magazine review of the Italian Victrix FTR rifle which Stuart is also shooting this season and although there is no mention of it in the text, the wide boy is shown in the main photograph at the start.
http://www.targetshooter.co.uk/?p=2046
Finally, a lot depends on what you use in F-Open. A 6BR with 105s or 6.5X47 Lapua with 123s or the 130 Hybrid puts a lot less energy and torque into the combo than a 7mm WSM wildcat with 180/195s, or a 300WSM with 230s!