Yes, the 3401 was my first and only polisher. It has a learning curve,
but let it teach you how it should be used.
Most people start with say a PC and then upgrade to the Flex etc. I was not of this mindset. I was going in so I bought the best from the start. Why not? I would end up spending extra if I went the aforementioned route.
I started with the 6.5" pads on the factory plate and found it a little tough to use, as it walks quite a bit. Keep it flat at all times otherwise it will walk on you. Once you get a hang of it you can use it in more ways. For example, for A pillars and thin panels I use the edge of the pad only as instructed by Mike Philips.
I then got the 4" lake country backing plate "adapter" and the 5" Hybrid pads. It changed the way I looked at this polisher. Its much smoother to use, does not walk unless you really tip it and such. Now it was even more easier to do thin panels.
Key is: Keep the pad flat at all times with some pressure(on the head) when using it. I do not exceed speed 5. As always do not stop in one spot for too long. It is a rather powerful machine.
Do not hold the polisher too far out from you, keep it close to you. This way the pad will not walk at all as you have control on it. I remember seeing a video where Mike and Bob from flex demonstrate this as well.
All machines have their pros and cons. Rupes does a few things better than the flex, while the flex does few things better than the Rupes.
You got the flex and you will love it, its a workhorse, will never stall, and will cut through defects in no time. :dblthumb2:
Edit: Look around for threads that talk about "oiling the felt ring" and such -
be proactive rather than reactive and learn as much as you can.
Look for and get the 4" backing plate and 5" hybrid pads. They are a match made in heaven.