1. I can keg a full 5 gallon batch. My glass carboy always lost some in blowoff or sediment. Now I fill the keg completely.
A definite plus with plenty of head space. Before I started kegging, I would brew & bottle 6-1/2 gal batches. I miss the additional volume but NOT dealing with the bottling...
2. Much easier to clean. I can get my arm in with a scouring pad and easily sanitize it. My glass carboy needed a bent handle brush and often days of soaking to come clean.
I've had one of my FF for almost two years. It's starting to develop stain ring from the krausen and I have only ever used a soft sponge to clean the inside. That stain tells me the surface of the plastic is starting to degrade and is rough enough to become susceptible to staining. The plastic will continue to degrade and at some point will become a problem for infections. Plastic fermenters do have a useful end of life.
But in order to prolong the life of the plastic, as others have said, I would not use anything rough like a scouring pad for cleaning the inside. At most, use a soft sponge. I've even seen some never touch the inside and only use PBW to clean it but I haven't gone that far. That's a lot of PBW when you brew 2-3 batches a month...
1. Transferring wort from the kettle into the fermenter is harder. I have to stand on a step pouring about 6 gallons slowly to not make a mess and avoid pouring the trub in.
After flame-out, I elevate my BK up on a stand so the ball-valve of the BK is above the top of the FF. Place a large plastic funnel in the top of the FF. Take a sanitized paint strainer bag and drape it over the top of the funnel to filter out some of the hop/trub. Then use a length of tubing to drain the wort from the elevated BK into the funnel/FF.
But that's a pain too...
2. Thermometer port is neat but not needed and potential for leaks and contamination. Easier to measure the temp in the environment and assume the beer will be similar.
In my case, I like and use the thermowell. I have a temp controlled ferm chamber and have a temp probe in the thermowell. It's especially important to know wort temp before pitching. Though things will settle down and equalize over the next 12 hours or so.
3. The threads on the lid and bowl assembly get tough to unscrew after fermenting. I'll try some vegetable oil next time.
I have had trouble getting the collection ball off sometimes. I end up using a cheap rubber strap wrench to get it loose.
In 25 years of brewing, this is the most innovative equipment available at low cost to the home-brewer that I have seen. My friends and I think my beer is the best we have tasted. I still have my glass carboys, but if the FastFerment continues to work well, those will be going on Craigslist.
Cheers!
Wow. That's a long time to have been brewing beer!
I bet this plethora of information (good & bad) wasn't available when you first got into it.
I do like the FF as well. I've been critical at times of the product and company but they seem to have things straightened out and the cost is very reasonable compared to other products on the market.
I hope something I wrote is of use to you or for someone. Good luck!