Interesting thread.
When I laid my track 12 years ago, I got a few lengths of LGB flexitrack from GRS and asked about the need for a rail bender. They told me not to bother unless I was going to have very tight curves. I laid all my code 332 track (a mix of LGB, Aristo and Tenmille) track without using a rail bender. I experienced no major problems, though I screwed the track down to concrete block foundations to stop it wandering. The only issues I had were where I had to have rail joints on two of my curves. In one case, inserted a new length of track to avoid having the joint on a curve (see
https://riksrailway.blogspot.co.uk/2008/08/progress-report-15-beeston-castle-is.html - about half way down) and with the other I tweaked the two offending ends of both pieces of track with a jim crow made by a fellow forumite ( see
https://riksrailway.blogspot.co.uk/2014/04/how-i-ironed-out-some-kinks-in-my-track.html ).
You can invest in a rail bender if you wish, but as the chap at GRS told me, you could buy another couple of lengths of track instead.
Rik