I love this brush when I first got it. Works great to blend in foundation around the nose area. It has very soft bristles and is of high quality. BUT...
I had so much gunk left after thoroughly cleaning it with makeup cleaner and it smelled so bad because the shorter bristles are so dense that it doesn't completely dry properly. UGH!! I've tried removing the gunk with oil cleanser to emulsify the foundation gunk and then using the antibacterial Sephora makeup brush cleanser and still...it smells after thorough drying. I think I will try dipping the bristles into alcohol and see if that kills off the bacteria smell and help it dry quicker. My makeup artist friend does that will all her brushes after each client.

$16 on the Sigma site - I put that as a 2 lippie because there are cheaper brushes out there but compared to MAC or Bobbi Brown or NARS brushes, $16 is nothing.
I am a huge fan of Sigma's Sigmax brushes, in fact, they are the only ones I use for fdtn regularly. I also own the original Prescriptives paddle brush (which has lasted me literally for 12 yrs) and am waiting on my Real Techniques order.
Firstly, the entire Sigmax range is fantastic. I have the F80 and the F82, and they have lasted me about 3-4 yrs and still going strong.
The hairs are synthetic which is perfect for fdtn as the bristles do not soak up fdtn. This makes them easier to clean, and you don't waste product. The bristles stay soft and easily reshaped after cleaning.
The handle is heavy and easy to hold. The shine has slightly come off mine but the name of the brush is still on. The handle is the right length so that it is easy to store.
Now on to the F88 specifically. Because it is flat, you can stipple with it. Because it is angled, you can swipe/blend with it. The sharp angle makes it easy to get product under the eyes and around the nose, you can blend out under eye concealer easily. It doesn't buff as well as the F80 due to the angle. But it is more comfortable to hold than the F80 due to the angle, so you can sorta hold it like a pen, and your wrist will be at a comfortable angle.
The F80 is probably still my 1st favourite, and I reach for that most often. But this one is my 2nd fave and a really great brush for a cheap price which will last ages.

More about me:
Asian normal skin - tending towards combination in summer
Was acne-prone for years
Foundation preference is to look as yellow as possible, absolutely nil pink
MAC NC-30, Shiseido O60, BeneFit Champagne, Bobbi Brown #4, MUFE Sand/Desert
Sunscreen everyday - alternating between Sofina and Invisible Zinc