Flashimage works well for flashing recoveries and kernels before a ROM. I've used it and it works well & as advertised, but u can't just enter recovery to restore a backup with it (need fastboot). I've used Cwm 220.127.116.11, Cwm Touch 18.104.22.168 (no usb mount/charging), and TWRP 2.0RC1 (with & w/o Dumlock).
Now, imo, I don't prefer to rely on FlashImage with S-On and think that all new HTC Unlocked/S-On users need to get experience flashing & booting to recovery via fastboot command prompt. This avoids most of the issues people experience like "my phone boot loops" & "flashed rom, now my phone stuck at white screen" etc. If ur using the correct fastboot commands all the recoveries I mentioned work pretty much the same minus the Touch features.
People run into problems not fully understanding these "workaround apps" (flashimage & Dumlock) even though the directions are well written. I just think some newcomers jump on these shortcuts and end up back to using fastboot anyway.
Currently I am using the TWRP 2 w/Dumlock and like that I can flash w/o fastboot (& restore nand backups too). If u don't follow steps correctly u can screw ur boot and have to use fastboot to reload recovery & restore backup. Other than fastbooting to recovery its the only way to fully restore a nand backup (b/c kernel flash). Note: u don't have to use Dumlock, but its part of the newer version if u want to.
I personally like the Touch screen version of Cwm & haven't had any issues other than the Usb issues I mentioned. I may give the Universal Dumlock option a go since it can be used with Cwm, but it won't be baked into the recovery. Also, I read that Agrabren left Team Win so future development of TWRP may be limited.
There's a lot of opinion in my post, but I hope I answered your question.
I'll also point out my guide/flashing notes & ROM/recovery issue (scenarios) in my signature have some detailed examples of what I did when using / flashing roms etc.
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