One big key is how you feed the machine. Improper feeding can create a lot of frustration and do a lot of damage to hitters' timing, thereby defeating the whole purpose. Not to be self-promotional, but I have a video blog post coming out late Friday afternoon that will illustrate some of the issues, how to correct them, and how to hit off a machine when it's not being fed properly. It will show up on my Life in the Fastpitch Lane blog, and will be linked in the "Ken's Blog Posts" forum below. Stay tuned...
If you feel you can't pitch that fast, set up closer to the plate. My kid's hitting instructor and her coach don't pitch from the distance a girl would during the game during practice. Maybe try that before shelling out for a pitching machine.
When you say front toss do you mean front toss on the field? Or in a cage? My daughter goes to a hitting instructor once a week and works front toss and tee. I just don't feel she or the girls on the team get enough pitches to them to get used to hitting higher speeds. Or even hitting lower 40s speed with power. I intend to share the machine with the team but want it to help and not be a hindrance. They've tried live pitching by our pitchers, who are very good pitchers, but it hasn't worked out very well.
Front toss is great, but the problem with hitting is not reaction time itself. It's reaction time caused by speed. That's the one thing that a pitching machine can provide that tee, front toss & side toss cannot - the actual speed of a live pitch. Reaction time is not a problem independent of speed, else it would be hard to hit fungos. Gotta hit fungos or self-toss in a fraction of a second, but it's not too hard. The problem is the speed (and change of speed and movement).
I'm not therefore endorsing the investment into a hitting machine. They're expensive. But I do believe that machines can be very helpful provided that the hitter is being instructed correctly and doesn't fall into problems caused if the machine is being used incorrectly. The instructor needs to understand sequence and find a way to get the hitter in sequence off a machine, or else you could cause real problems. IMO, key here is getting hitter to anticipate when the ball comes out of the chute so hitter is moving out as ball is coming in. If move out is too early or late, you can screw up your swing without knowing what hit you.