We've got one. We bought it in October and have been getting to know it. It's our first motor boat (having previously had a sailing yacht) so maybe we don't have as much to compare it to. For us, it represented good value for money and offered pleasant accommadation down below while having good space and layout up on deck. It feels comfortable at sea although, like comparable vessels, the bow doesn't have much grip on the water when handling at close quarters so it's prone to being blown off by the wind: it's nice to have the bow thruster. Engine choice will be a factor too. You don't want it underpowered.
We bought it secondhand from Sealine and have been impressed with their no-quibble approach to the few warranty repairs we sought.
Our usage is coastal trips and cross-Channel in reasonable weather, and we have a young family.
You haven't filled out your profile so we cannot see how you intend to use it or your current experience etc. Folks on here will be more likely to offer comments if you do fill it out, and I've found the advice on this forum to be good.
Some people have bad things to say about Sealines but we spent quite a lot of time wondering round marinas and asking Sealine owners for their views, which were favourable.
In short, if you want an all-weather, go-anywhere motor yacht, then you won't want a Sealine. But, if you want to do the typical stuff which families do, then you may well like the S34.
You can order back-copies of the MBM review for a small a few pounds (it gives the S34 a good write-up).
You would have been better to post this question on the Motorboat forum.