I've been riding one for the last three years and I agree with everyone else up to a point. I think you need to take a good look at how the club you ride with lays out sections at your level. If the sections are designed where you have a reasonable run at the bigger ups, then by in large you'll love the bike. On the other hand, if you have to attack steps with little to no run or they design sections with multiple steps one after another, it can make life "interesting". The Beta 200 is not nearly as "rev sensitive" as a 125, but with a bigger guy you do have to be really spot on with the clutch on short approaches. Another downside comes with altitude. We have trials ranging from about 3000 ft all the way to over 7000, and at the higher elevations the extra grunt of a big bike would really come in handy (I weigh a bit over 200lbs).
Not trying to turn you away from one as I've loved my owning my bike and it's been great to ride. I just wanted to point out a couple of other things to consider.
Joe