If the Arenal volcano were actually erupting, this would be a pretty spectacular place. It is architected so that you can look out your room's window or from your patio hot and see the tip of the cone, or sit at the "wet bar" and watch similarly.
But the eruptions and action apparently stopped 2 years ago. So one has to judge this hotel and town on its merits.
The best way to describe the rooms at the Mountain Paradise is Poconos in Costa Rica; over-the-top, low-quality, kitsch. The rooms have funny showers made of stone with a waterfall coming over your head; ours even had a complementary live frog hopping around and a giant cockroach during the night. The enormous king bed has a funny curtain around it with giant logs overhead. And of course there is an air conditioner and a flat screen TV.
The guests are generally whit trash. At 10:15PM, I just witnessed a 300+ lb American man, who's every 5th word is a curse, rearrange the lounge furniture, sit in a chair, and fragment it to smithereens. He then discussed with his family how they all had been drinking continuously since 10AM, and whether to report the destruction to the staff.
The hotel itself organizes tours with an insane markup.
The town also pretty much sucks; it has been overrun with busloads of tourists (the scene at the hot springs in the evening is insane).
So, if you're looking for an alternative to Fort Lauderdale for Spring Break, you could consider this. If you were looking for a place that brings out the quality of Costa Rica, avoid this place completely.
A one virtue of this place is the staff, who smile, laugh it off and seem to get on.