we've got an F machine - and yes it is actually called the F machine. I bit the bullet and bought it after i rtealised that mking one whilst not overly complicated was a bit ofa stretch for me. Was it worth it? well JJ my other\half would be better placed to give it an 'O' rating as i'm merely the Organ grinder......
but from the sidelines i woudl say YES it is a useful addition to the toy chest. It doesnt get used at every 'play' session but without getting too graphic , a set of towels are needed when its used in conjunction with other bits n pieces like a wand, or a bit of electro play. Would she ever use it 'solo'....probably not, unless i was away/out of action for a while as its not like whipping a vibe out of a drawer and merrily getting involved .....dont get me wrong its easy enough to control, but there is a degree of setting up, ie/ adjusting it to the right angle/height etc. swapping attachments on ours is easy as it just uses vac u lock dildos
i spent a while looking at prices and also at the home made offerings and learnt a fair bit. Cheapies will be held back by the power of the motor, it isn't about how fast t can go, but how powerful the motor is for thrust( torque)...there's a heck of a lot of resistence when a woman is in orgasm.....we liked teh idea of the thrusting action rather than the sybian type which is more clit focused, but a combination of teh two would be great and at some point i may adapt what we have.
each will no doubt have their own opinion, but i'd suggest that it would be hard to find a reasonable machine under about £400. if you are edver looking seriously, then the things to maybe look at are@ is the stroke length adjustable, how usable is it - ie/ how is it used, like a saddle or is it more vaiable - doggy, lying down front/back, how powerful is it, how adjustable is the speed ( bear in mind that many machines will say they do x strokes per min, but thats without any resistance), and are the attachments available/interchangeable......happy to answer any thing else if folks are interested/intrigued.